Members of Libya's national assembly have elected Deputy Prime Minister Mustafa Abu Shagur as the country's next prime minister.

In a run-off vote he narrowly beat Mahmoud Jibril - who served as interim PM following the uprising against Col Muammar Gaddafi last year.

Mr Shagur is a respected optical engineer with a long history of opposition to Col Gaddafi.

He has pledged to make security a priority during his 18-month tenure.

Mr Jibril comfortably won the first round of the vote, with 86 to 55 votes. But in the run-off, Mr Shagur won 96 votes, two more than Mr Jibril.

Mr Shagur's victory was in part due to the support of deputies from the Muslim Brotherhoods' Justice and Construction Party, AFP news agency says.

The election came a day after the killing of the US ambassador to Libya, and three others, in an attack on the consulate in the country's second city, Benghazi.

Mr Shagur studied at the University of Tripoli before moving to the US, where he earned a PhD and worked as an academic and optical engineer.

He returned in 2011 to become an adviser to the National Transitional Council, which was formed during the revolt that ousted Gaddafi.

Last November, he was appointed deputy to Prime Minister Abdurrahim al-Keib.

The 200-member national assembly was elected in July, in the first free polls in decades.