As authorities scramble to establish what happened to Malaysia Airlines Flight 17 in Ukraine, U.S. officials on Friday pointed the finger toward pro-Russia rebels.

U.S. Ambassador to the United Nations Samantha Power told an emergency meeting of the U.N. Security Council that the plane was "likely downed by a surface to air missile ... operated from a separatist-held location in eastern Ukraine."

She said if pro-Russian separatists are responsible for shooting down the plane with a missile, it cannot be ruled out that Russia offered help to operate the system,

Separatist leaders also boasted on social media about shooting down the plane and later deleted those references, she said.

On board were 298 people, none of whom survived the crash, she said. Three were infants.

A preliminary classified U.S. intelligence analysis has concluded that the missile that hit Flight 17 most likely was fired by pro-Russian separatists inside eastern Ukraine, according to a U.S. defense official with direct access to the latest information.

The official declined to be identified because of the sensitivity of the information.

Power had tough words for Russia, saying it had not lived up to its commitments to ease tensions and halt the flow of weapons over the border to the rebels in Ukraine.

Ukrainian Prime Minister Arseniy Yatsenyuk earlier blasted the "terrorists" he blamed for shooting down Flight 17 over Ukraine a day earlier, with 298 people aboard.

He called on all governments to back the investigation and "to support the Ukrainian government to bring to justice all these bastards who committed this international crime."

Russia, Ukraine trade accusations

Since the Malaysia Airlines jet fell from the sky above eastern Ukraine on Thursday, Russia and Ukraine - which routinely uses the word "terrorists" to describe pro-Russian rebels - have traded blame and accusations.

"Terrorists have killed almost 300 persons with one shot," Ukrainian President Petro Poroshenko said Thursday. "Among them are women, children, citizens of different countries of the world."

Russian President Vladimir Putin pointed the finger back at Ukraine, blaming its recent tough military operations against separatists for the volatility in the region.

But Ukrainian Foreign Minister Pavlo Klimkin rejected that claim, telling CNN it was up to Russia to stop the flow of heavy weaponry across Ukraine's eastern border and push the separatists to embrace a cease-fire.

He also dismissed any suggestion that Ukrainian forces may have been involved in Thursday's tragedy.

"There was no way our forces could be engaged in any way in this incident," Klimkin said, adding that Ukraine did not have any military assets in the area that could have shot down MH17.

Klimkin says Ukraine intercepted telephone calls between "terrorists" at the time the plane was shot down.

Yatsenyuk called for a U.N. Security Council meeting to be held and for all nations to do everything they could to stop what he said was not now just a war in Ukraine or Europe, but a "war against the world."

Meanwhile, international inspectors headed to the crash site Friday tasked with finding the plane's flight data recorders, which may lie amid the human remains and debris strewn across fields near the town of Torez.

Ukrainian government officials said 181 bodies had been found.

The latest information from Malaysia Airlines indicates that the Netherlands has suffered the harshest blow, with at least 189 of its citizens among those killed.

Experts have voiced concern that the crash site has not been properly secured, making the recovery of bodies and collection of evidence difficult.

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