UPDATE 1:40 PM EST: Reuters reports 23 U.S. citizens are among the 300+ people killed after a Malaysia Airlines flight was reportedly shot down in Ukraine near the Russian border.

UPDATE 12:40 EST: Reuters is reporting that Ukrainian officials claim the plane was shot down by pro-Russian rebels:

The Boeing 777 came down near the city of Donetsk, stronghold of pro-Russian rebels, interior ministry official Anton Gerashchenko said on Facebook, adding it was “shot down with a Buk anti-aircraft system by terrorists” – the term the Kiev government uses for militants seeking to unite eastern Ukraine with Russia.

It's important to note that there has been no further confirmation on this, and Russian officials have denied any involvement or knowledge.

A Malaysia Airlines Boeing 777 with 295 people aboard was reportedly hit by a missile and crashed Thursday in Ukraine near the Russian border.

Anton Gerashenko, an adviser to Ukraine's interior ministry, says on his Facebook page the plane was flying at an altitude of 33,000 feet when it was hit by a missile.

Malaysia Airlines said on Twitter that it "has lost contact of MH17 from Amsterdam. The last known position was over Ukrainian airspace."

It is being reported that the plane was 30 miles from Russian airspace when it began to go down. The burning wreckage of the plane was found on the ground in Ukraine.

There were 280 passengers and 15 crew members aboard.

The flight was en route to Kuala Lumpur from Amsterdam, and crossed over a highly volatile area. It was apparently still on the Ukrainian side, though the exact location remains unclear at this time.

The unconfirmed video below claims to show a black plume of smoke pouring from where the plane crashed.

[CNN]