Two staff members at a school in Israel have been arrested after 10 teenagers on a school trip were killed in flash floods in the south of the country.

Those detained on suspicion of death by negligence include the principal of the Tel Aviv-based pre-military academy, Israeli media report.

The nine females and one male who died were swept away on a hike in the Negev desert following torrential rain.

Israeli PM Benjamin Netanyahu said the country was in mourning at their loss.

"The State of Israel grieves for the promising young lives that were cut off by the grave disaster in the Arava [region]. We embrace, with pain, the grieving families, and pray for the speedy recovery of the wounded," he said.

'She slipped away'

The disaster happened during a hike intended as a bonding exercise for the students who were due to start the Benny Tzion pre-military academy.

They were part of a group of 25 people, including staff, who went on the trek in Nahal Tsafit, south of the Dead Sea.

Authorities had issued warnings to avoid the area because of the risk of flash floods following two days of heavy rain.

A huge operation including police, the air force and local search-and-rescue teams was launched after the alarm was raised on Thursday afternoon.

The bodies of the 10 dead students were recovered by Thursday night. They were all aged between 17 or 18.

The teens who died were due to start a preparatory programme for the army

Police arrested two members of staff and put a third under house arrest as investigations continued.

One of the survivors said a wave that was at least three metres high (10 feet) hit his group, and that he had seen bodies floating in the water.

"I was holding on to one of my friends really tight," the father reported the unnamed student as saying. "But we couldn't cope with the massive flow of water. She slipped away from me in front of my eyes."

The students who lost their lives came from across Israel and funerals were due to be held on Friday.