PHOENIX — Sen. John McCain (R-Ariz.) has reportedly promised “incredible repercussions” if it is proven a Malaysian passenger jet was shot down over Ukraine.

According to comments posted by the Huffington Post, McCain did not commit to reports the plane had been shot out of the sky as it approached Russian airspace.

“To leap to conclusions could be very embarrassing and really inappropriate until we have more information,” he told NBC’s Andrea Mitchell. “But there have been, as you mentioned, previous incidents of shot down of Ukrainian aircraft. This was an airliner headed towards Russian air space. And it has the earmarks, and I’m not concluding, but it has the earmarks of a mistaken identification of an aircraft that they may have believed was Ukrainian. “If that’s true, this is a horrible tragedy event which was certainly unanticipated by anybody, no matter who they are,” he said. “And there will be incredible repercussions if this is the case. Exactly what those will be will have to be determined by how we find out who was responsible.” McCain added, “If it is a result of either separatists or Russian actions mistakingly believing that this was a Ukrainian warplane, I think there’s going to be hell to pay and there should be.”

On Wednesday evening, a Ukrainian fighter jet was shot down by an air-to-air missile from a Russian plane, Ukrainian authorities said Thursday, adding to what Kiev says is mounting evidence that Moscow is directly supporting the separatist insurgents in eastern Ukraine. Security Council spokesman Andrei Lysenko said the pilot of the Sukhoi-25 jet hit by the air-to-air missile was forced to bail after his jet was shot down.

Pro-Russia rebels, meanwhile, claimed responsibility for strikes Wednesday on two Ukrainian Sukhoi-25 jets. The Ukrainian Defense Ministry said the second jet was hit by a portable surface-to-air missile, but added the pilot was unscathed and managed to land his plane safely

Moscow denies Western charges that is supporting the separatists or sowing unrest in its neighbor. The Russian Defense Ministry couldn’t be reached for comment Thursday about the Ukrainian jet and Russia’s foreign ministry didn’t respond to multiple requests for comment.

Earlier this week, Ukraine said a military transport plane was shot down Monday by a missile fired from Russian territory.

The rebels are known to possess portable anti-aircraft rocket launchers, but Ukrainian officials say that kind of weapon would have been unable to reach Monday’s plane at the altitude at which it was flying Monday. Aviation experts, however, have questioned whether the stricken transport plane was flying at the altitude Ukrainian officials had claimed.

The Associated Press contributed to this report.