NEW YORK, July 17 -- The crash of a Malaysian passenger plane in Ukraine on Thursday was shrouded in mystery of a deliberate attack, with Kiev trading accusations of blame with separatists and Moscow.

U.S. media reported that the Boeing 777 jet of the Malaysia Airlines, with 295 people onboard, was shot down by a missile when flying over eastern Ukraine en route from Amsterdam to Kuala Lumpur.

A radar system saw a surface-to-air missile system turn on and track an aircraft right before Malaysian airliner MH17 was shot down, CNN reported, citing an unnamed official.

A second system saw a heat signature at the time the airliner was hit, the official added.

The United States is analyzing the trajectory of the missile to try to learn where the attack came from and has not determined who was responsible, according to the report.

The Washington Post quoted a U.S. official as saying that American intelligence agencies had confirmed that the plane was shot down by a surface-to-air missile.

The official, who was not authorized to speak on the record about an early intelligence assessment, told the newspaper that government analysts were scrambling to determine who fired the missile.

U.S. Vice President Joe Biden said on Thursday it appeared that the crash near the Ukraine-Russia border was not an accident and that the passenger jet apparently was "blown out of the sky."

"This is truly a grave situation," Biden said.

A Ukrainian official accused pro-Moscow rebels, aided by Russian military intelligence officers, of shooting down the plane with a long-range, Soviet-era SA-11 ground-to-air missile.

"Terrorists" used a ground-to-air missile to bring down the Boeing 777 passenger plane, the official said.

Meanwhile, a rebel leader said Ukrainian forces shot the airliner down.

"The plane was shot down by the Ukrainian side. We simply do not have such air defense systems. Our MANPADs have a firing range of only 3,000 to 4,000 meters, while passenger jets fly at a much higher altitude," Interfax quoted him as saying.

Russian President Vladimir Putin also laid the blame on the Ukrainian government.

"There is no doubt that the country on whose territory this terrible tragedy happened bears responsibility," Putin was quoted by Ria Novosti news agency as saying.

"This tragedy would not have happened if there was peace in the country, if military operations had not resumed in the south-east of Ukraine," he added.

The claim was rejected by Ukrainian President Petro Poroshenko.

Poroshenko said the country's armed forces did not fire at any flying object in the region where the plane went down.

UN Secretary-General Ban Ki-moon on Thursday expressed deep condolences over the crash and called for a "full and transparent international investigation" into it.

"There is clearly a need for a full and transparent international investigation," he said. "For the moment, I offer my deep condolences to the families and loved ones of the victims and people of Malaysia."

The UN Security Council will hold an emergency meeting Friday to discuss the incident, officials said.