A Ukrainian official says a Malaysian passenger plane carrying 295 people was shot down today over a town in the east of the country.
Anton Gerashenko, an adviser to Ukraine's Interior Minister, said on his Facebook page the plane was flying at an altitude of 33,000 feet when it was hit by a missile fired from a Buk launcher.
Ukraine's president says his country's armed forces did not shoot at any airborne targets.
President Petro Poroshenko says Thursday "We do not exclude that this plane was shot down, and we stress that the Armed Forces of Ukraine did not take action against any airborne targets."
Poroshenko said "We are sure that those who are guilty in this tragedy will be held responsible."
A similar launcher was seen by Associated Press journalists near the eastern Ukrainian town of Snizhne earlier Thursday.
Malaysia Airlines said on its Twitter feed that it "has lost contact of MH17 from Amsterdam. The last known position was over Ukrainian airspace.
We will bring you more details throughout the day as they come in.