WILMINGTON, Del. — President Barack Obama said Thursday that the passenger plane downed over Ukraine “looks like it may be a terrible tragedy” and his top priority is finding out whether American citizens were on board while Sen. John McCain fired some harsh words Russia’s way.

Obama also offered help to Ukrainian President Petro Poroshenko, who called the downing of the Malaysia Airlines plane carrying 295 people an act of terrorism.

McCain said if it’s proven Ukrainian separatists did shoot down the plan, Putin should pay.

“It’s an outrageous and incredible act of terrorism that people [should] be held responsible and not only be people directly responsible, but indirectly,” McCain said, according to Roll Call. “And if these are … separatists, which are also Russian, Vladimir Putin should be paying a heavy price. But I am not concluding yet that until we find out all the information.”

During an interview on MSNBC, he also said “I think there’s going to be hell to pay and there should be.”

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An Associated Press journalist counted at least 22 bodies at the crash site about 25 miles from the Russian border, where government and pro-Moscow separatists have been fighting.

Anton Gerashenko, an adviser to Ukraine’s interior minister, said on his Facebook page that the plane was flying at an altitude of 33,000 feet when it was hit by a missile fired from a Buk launcher.

Obama press secretary Josh Earnest said Obama was on a phone call with Russian President Vladimir Putin when news of the downed plane broke. Earnest and the Kremlin said Putin mentioned those early reports in the call, but provided no details of what the two leaders said about it.

“The world is watching reports of a downed passenger jet near the Russia-Ukraine border,” Obama said later as he took the stage for a speech in Delaware to discuss transportation funding. “It looks like it might be a terrible tragedy. Right now we’re working to determine whether there were American citizens on board. That is our first priority.”

The rest of the phone call between Obama and Putin was dedicated to the general situation in eastern Ukraine, and recent U.S. sanctions against Russian individuals and companies.

The Federal Aviation Administration had warned U.S. pilots earlier this year not to fly over portions of the Ukraine in the Crimea region, according to notices posted on the agency’s website.

The notices were posted on April 23. The U.N.’s International Civil Aviation Organization and the aviation authorities in most countries issue similar notices for areas where unrest or military conflict creates a risk of being shot down.

The FAA had not issued any new warnings Thursday afternoon in the immediate aftermath of reports that a Malaysian airliner had been shot down over the Ukraine.

Thursday afternoon, U.S. officials said the plane was shot down with a surface-to-air missile.

“Not an accident. Blown out of the sky,” Vice President Joe Biden said, according to The Hill.

CONTRIBUTING: ASSOCIATED PRESS