Poroshenko, speaking to CNN’s Christiane Amanpour, pleaded for international solidarity against the rebels fighting the government in Kiev.
“I don’t see any differences” between 9/11, the Lockerbie bombing, and the attack on Flight MH17, Ukrainian President Petro Poroshenko said.
Such terrorism is a danger to the “whole world” and to “global security,” he said.
Obama, speaking at nearly the same time in Washington, called on Russia to rein in the rebel fighters believed by many international leaders to be responsible for downing the passenger jet and killing all 298 aboard.
He said Russia has so far failed to stop the rebels from impeding investigators at the site and accused them of treating remains poorly and removing evidence from the site.
“What exactly are they trying to hide?” he said.
Despite the stern tone of the Ukrainian and U.S. leaders, the spokesman for a team of European monitors at the site said rebels have granted monitors and experts nearly “unfettered access” to wreckage Monday.
“Today we have three Dutch forensics experts with us, and they’re getting pretty much unfettered access,” Michael Bociurkiw, the spokesman for monitors from the Organization for Security and Co-operation in Europe, told CNN’s Chris Cuomo.
The rebels even provided some perimeter security to keep journalists at bay, creating a “dome of tranquility” for the OSCE monitors, Dutch forensic experts and a handful of Ukrainian aviation experts now at the scene, Bociurkiw said separately in a briefing for reporters hosted by the Ukrainian Crisis Media Center.
On Sunday, Bociurkiw had said access to the site had improved after an initial welcome by rebels that he had described as hostile.
But Ukrainian officials and President Barack Obama said Monday that rebels continued to stymie the investigation, hindering access to the site and tampering with evidence.
“What exactly are they trying to hide?” Obama said.
Bociurkiw said it remains difficult to get to the site, and fighting between rebels and government forces in Donetsk could have a significant impact on the investigation, he said.
Ukrainian officials and rebel forces reported fighting around the train station in Donetsk on Monday, with city officials reporting damage to a residential building near the train station and a nearby market catching fire after it was shelled. The train station, however, remained in operation, the city officials said.
With air service out, an interruption in train service could hinder the ability of investigators to get into and out of the site, Bociurkiw said.
“That’s very crucial, because it’s the only remaining transport link between here and really the outside world.”
It could also affect efforts to transport the remains of the 298 people who died when Flight 17 plummeted to the ground — the apparent victims of a surface-to-air missile strike that U.S. officials have said appeared to be launched from rebel-held territory near the Russian border.
As of Monday, workers had recovered 282 bodies, with 251 stored in refrigerated train cars near the crash site.
Dutch forensics experts were “more or less” satisfied with how the bodies were being stored,” Bociurkiw said.
Rebels were expected to allow the train to travel to the eastern city of Kharkiv at 7 p.m. (noon ET), according to Ukraine Vice Prime Minister Volodymyr Groysman.
Ukrainian government officials have said the bodies will eventually be taken to Amsterdam. Most of those who died in the crash were Dutch.
Bociurkiw had no information about the status of a team of international crash experts staging in Kharkiv to inspect the debris.
Earlier, the Ukrainian government issued a news release saying the experts had reviewed photos of the crash scene.
Another team from the Netherlands remains in Kiev, according to the Dutch Foreign Ministry.
Dutch Prime Minister Mark Rutte met with relatives and friends of victims Monday, calling the session filled with sadness and “very touching.”
“All of the Netherlands is feeling their fury. All of the Netherlands is sharing their deep sadness, and all of the Netherlands is just gathering around all the next of kin,” he said.
‘An outrage made in Moscow’
Meanwhile, intelligence analysts were working furiously to determine whether Russian officials had any direct involvement in the downing of the jetliner — an accusation Moscow has strongly denied.
U.S. analysts are examining phone intercepts, social media posts and information gathered on the ground to see what role, if any, Russian officials may have played, according to two U.S. officials directly familiar with the latest assessment who declined to be identified because of the sensitivity of the situation.
“We are trying to determine if they manned it, advised, or pulled the trigger,” one of the officials told CNN.
U.S. Secretary of State John Kerry said there’s no shortage of evidence that pro-Russian rebels shot down the jet.
There’s video of a launcher with one surface-to-air missile missing, imagery showing the firing and intercepted calls with rebels claiming credit for the strike, Kerry said.
“We know from intercepts … that those are in fact the voices of separatists,” he told CNN’s “State of the Union” on Sunday. “And now we have a video showing a launcher moving back through a particular area there out into Russia with at least one missing missile on it.”
British Prime Minister David Cameron didn’t mince words either on who was to blame. In an op-ed in The Sunday Times, he called the plane crash and its aftermath “an outrage made in Moscow.”
Russian President Vladimir Putin fired back with a video statement posted on the Kremlin’s official website early Monday, arguing that his country has been pushing for peace in Ukraine.
“We have repeatedly called on all parties to immediately stop the bloodshed and to sit down at the negotiating table. We can confidently say that if June 28 fighting in eastern Ukraine did not resume, this tragedy most likely would not have happened,” he said. “However, no one should have the right to use this tragedy to achieve selfish political objectives. Such events should not divide but unite people.”
He stressed that safety must be guaranteed for international experts investigating the crash.
“We must do everything to ensure their work has full and absolute security (and) ensure necessary humanitarian corridors are provided,” Putin said.
On Monday, Russian officials floated the possibility that a Ukrainian fighter jet might have downed the plane.
Russian monitoring showed a Ukrainian Su-25 fighter jet flying along the same route and within 3 kilometers to 5 kilometers (1.9 miles to 3.1 miles) of Flight 17, Lt. Gen. Andrei Kartapolov of the Russian Army General Staff said at a news conference, Russian state media reported.
“We would like to know why the Ukrainian plane was flying along a civilian route on the same flight path as the Malaysian Boeing,” Kartapolov said, according to the reports.
Pro-Russian rebels have also denied responsibility for the shootdown.
In an interview with Cuomo broadcast Monday on CNN’s “New Day,” the self-declared rebel Prime Minister in Donetsk, Alexander Borodai, said he believed Ukrainian forces either shot the plane down with a surface-to-air missile or, as the Russian general suggested, one of its own fighter jets.
“We didn’t have motives and desire to do that, and it is obvious that Ukrainians have them,” he said. “I can’t say about desire, but motive is obvious that the crash of this plane was beneficial to them.”
Black boxes found?
Borodai also told Cuomo that he believes rebels have retrieved the jet’s black boxes, but that he couldn’t say for sure because he is not a technical expert.
Earlier, Borodai said the devices are under guard in the region. They will not be given to Ukrainian officials, he said.
Reuters distributed video Sunday of what appeared to be an inflight recorder found by a worker in a field. The agency labeled the video, shot Friday, as showing one of the two flight data recorders from Flight 17.
Some Malaysian investigators flew to the Ukrainian capital of Kiev on Saturday. But Malaysia’s official news agency said they were still negotiating with rebels over access for their team.
Law enforcement officials from the Netherlands, the United States and Australia will help with the investigation led by the Ukrainian government.
Two FBI agents have arrived in Kiev, a senior U.S. law enforcement official said. An investigator from the National Transportation Safety Board was also there.