Israel has sent a specialist search and rescue team to help find any survivors from a helicopter which crashed into a mountain in central Romania, killing at least four of the seven soldiers on board.

The CH-53 military transport helicopter was carrying six Israelis and one Romanian on an aviation training exercise near the town of Zarnest when it is thought to have encountered bad weather.

Officials have not confirmed that the wreckage has been found, but it is believed all those on board have been killed.

An Israeli military spokesperson said a delegation of 80 people, including medical staff and body identification experts had arrived in Romania.

He said: "Extensive searches are currently taking place on the scene."

Romania police spokesman Ciprian Aldea said there were parts of the helicopter and human remains around the crash area.

He said: "It is a very difficult area, very rocky.

"You can't reach the area without the appropriate search equipment."

The cause of the disaster is unconfirmed, but onlookers reported seeing smoke and flames coming from the helicopter.

There have been several other accidents involving CH-53 helicopters in Israel, including a crash in 1997 on the border between Israel and Lebanon, in which 73 people died.