By Irene Klotz

CAPE CANAVERAL, Fla. (Reuters) - An unmanned Russian cargo ship loaded with more than 2-1/2 tons of food and supplies for the International Space Station broke apart about six minutes after liftoff on Thursday, Russia's space agency Roscosmos said in a statement.

A Soyuz rocket carrying the Progress capsule blasted off from the Baikonur Cosmodrome in Kazakhstan as planned at 9:51 a.m. EST, a NASA TV broadcast showed.

But ground control teams then lost radio contact with the rocket and most of the spacecraft fragments burned in the dense atmosphere, Roscosmos said in a statement.

It added that the capsule was last confirmed flying at an altitude of about 190 km (118 miles) over the remote and unpopulated area of the Republic of Tyva.

The cause of the accident is under investigation.

The six-member crew aboard the International Space Station is not in any danger and has enough supplies for several months, NASA said.

Thursday’s launch was the fourth failed cargo run to the station in the past two years, including one previous Progress failure.

The accident comes at a critical time because SpaceX, one of two U.S. companies flying supplies to the station for NASA, has not yet returned to flight following a Sept. 1 launch pad accident.

SpaceX is awaiting approval from the Federal Aviation Administration, which oversees U.S. commercial space transportation, to fly as early as Dec. 16 with 10 satellites owned by Iridium Communications Inc.

SpaceX's next cargo flight for NASA is targeted for January. Orbital ATK and Japan's space agency also fly supplies to the station, a $100 billion laboratory that flies about 250 miles (418 km) above Earth.

Launch of a Japanese cargo ship is scheduled for Dec. 9.

(Reporting by Irene Klotz; Editing by Colleen Jenkins and Tom Brown)