At an emergency meeting of the U.N. Security Council, the U.S. pointed blame at the separatists, saying Washington believes the jetliner carrying 298 people, including 80 children, likely was downed by an SA-11 missile, and "we cannot rule out technical assistance from Russian personnel."
Both the White House and the Kremlin called for peace talks in the conflict between Ukrainian government forces and Russian-speaking separatists who seek closer ties to Moscow. Heavy fighting was reported less than 100 kilometers (60 miles) from the crash site, with an estimated 20 civilians reported killed.
Emergency workers and local coal miners recovered bodies from grasslands and fields of sunflowers, where the wreckage of the Boeing 777 fell Thursday.
About 30 officials, mostly from the Organization of Security and Cooperation in Europe, arrived at the crash site between the villages of Rozsypne and Hrabove, about 40 kilometers (25 miles) from the Russian border.
The rebels allowed the team to perform a very partial and superficial inspection. While the delegation was leaving under orders from the armed overseers, two Ukrainian members lingered to look at a fragment of the plane by a roadside, only for a militiaman to fire a warning shot in the air with his Kalashnikov.
The dead passengers were from nearly a dozen nations — including vacationers, students and a contingent of scientists heading to an AIDS conference in Australia — when the plane was shot down Thursday while flying from Amsterdam to Kuala Lumpur.
President Barack Obama, disclosing that one American was among those killed, called it "a global tragedy."
"An Asian airliner was destroyed in European skies filled with citizens from many countries, so there has to be a credible international investigation into what happened," he said.
In Kiev, Ukrainian Prime Minister Arseniy Yatsenyuk vented his anger in calling for an international investigation.
"We ask all respective governments ... to support the Ukrainian government to bring to justice all these bastards who committed this international crime," he said.
All sides in the conflict — the Ukrainian government, the pro-Russia rebels they are fighting and the Russian government that Ukraine accuses of supporting the rebels — denied shooting down the plane. Moscow also denies backing the rebels.
Russian Foreign Minister Sergey Lavrov dismissed accusations that Moscow could be behind the attack.
"Regarding those claims from Kiev that we allegedly did it ourselves: I have not heard a truthful statement from Kiev for months," he told the Rossiya 24 television channel.
At the Security Council, U.S. Ambassador Samantha Power said the missile was likely fired from a rebel-held area near the Russian border.
Power said that early Thursday, a journalist saw an SA-11 system — known in Russia as a Buk missile system — in separatist-controlled territory near Snizhne, "and separatists were spotted hours before the incident with an SA-11 SAM system close to the site where the plane came down."
"Separatists initially claimed responsibility for shooting down a military transport plane, and claimed responsibility and posted videos that are now being connected to the Malaysian Airlines crash," Power said. "Separatist leaders also boasted on social media about shooting down a plane, but later deleted these messages."
"Because of the technical complexity of the SA-11, it is unlikely that the separatists could effectively operate the system without assistance from knowledgeable personnel. Thus, we cannot rule out technical assistance from Russian personnel in operating the systems," she said.
Russian Ambassador Vitaly Churkin did not respond to the U.S. allegations.
Ukraine's Interior Ministry released a video purporting to show a truck carrying the Buk missile launcher it said was used to fire on the plane with one of its four missiles apparently missing. The ministry said the video was shot by a police surveillance squad at dawn Friday as the truck headed toward the Russian border.
There was no way to independently verify the video.
The entire Security Council called for "a full, thorough and independent international investigation, in accordance with international civil aviation guidelines, and for appropriate accountability." It stressed the need for "immediate access by investigators to the crash site to determine the cause of the incident."
Obama also called for such an investigation, adding: "The eyes of the world are on eastern Ukraine, and we are going to make sure that the truth is out."
He also called for a cease-fire in the conflict between the separatists and Ukrainian forces. At a Kremlin meeting, Russian President Vladimir Putin urged that "all sides in the conflict should halt their fighting and enter into peaceful talks," according to an official website.
On Thursday, Putin blamed Ukraine for the crash, saying Kiev was responsible for the unrest in its Russian-speaking eastern regions. But he didn't accuse Ukraine of shooting the plane down and didn't address the key question of whether Russia gave the rebels such a powerful missile.
Ukraine's state aviation service closed the airspace Friday over two border regions gripped by separatist fighting — Donetsk and Luhansk — and Russian airlines suspended all flights over Ukraine.
Luhansk, a rebel stronghold northeast of Hrabove, saw sustained fighting Friday as Ukrainian government forces reportedly retook part of the city from the rebels.
City officials estimated at least 20 civilians had been killed in shelling. One resident told The Associated Press that street-to-street fighting had continued into the night.
Defense Minister Valeriy Heletey said government troops had retaken the southeast section of the city.
There was uncertainty over whether Flight 17's flight data and cockpit voice recorders had been recovered.
Donetsk separatist leader Aleksandr Borodai said "no 'black boxes' have been found," although earlier in the day, an aide to the military leader of Borodai's group said authorities had recovered eight out of 12 recording devices from the plane. Since planes usually have two recorders, it was not clear what the aide was referring to.
At the sprawling crash site, lines of men — including about 70 off-duty coal miners — disappeared into thick, tall growth that reached over their heads as they conducted their search. One man fainted after finding a body. Another body was covered in a coat.
A large number of sticks, some made from tree branches, were affixed with red or white rags to mark spots where body parts were found.
Smashed watches and cellphones, charred boarding passes and passports were among the debris.
In the distance, the thud of Grad missile launchers being fired could be heard Friday morning.
Ukraine's government said it is already preparing for the bodies to be taken to the city of Kharkiv, 300 kilometers (190 miles) north of the crash site. But Andrei Purgin, a leader of the separatists, said they would go to the government-controlled Black Sea city of Mariupol.