Kerry says 'dangerous' violence in Libya 'must stop'

US Secretary of State John Kerry Tuesday called for a halt to the violence in Libya, saying the United States was working with Libyan leaders to end the unrest.

"It is dangerous and it must stop, and we are working very hard to find political cohesion," Kerry said.

"We are obviously deeply concerned about the level of violence in Libya," Kerry told reporters in Vienna, as he wrapped up two days of talks on Iran's nuclear programme.

"Every single day in the State Department we make assessments about the level of violence, about our personnel who are there, about our embassy," he said.

Libya's government said it is considering calling for international forces to help re-establish security after deadly clashes closed Tripoli airport, severing air links with the outside world.

Fighting between liberal and Islamist militias locked in a brutal power struggle forced the closure of the country's main international airfield, leaving the North African state feeling increasingly isolated.

On Monday, the United Nations announced it was evacuating its remaining staff from Libya because of the deteriorating security situation.

US special envoy David Satterfield was working closely with special envoys from countries such as Britain "on how we can transition Libya away from this militia violence, which is threatening the airport at the moment," Kerry said.

Kerry said the violence was not threatening "broadly every interest within Libya, but it is dangerous and it must stop".

"We will continue to stay very, precisely focused upon it," he added.