Libya: Haftar forces arrest rival commander in Derna

Forces loyal to Libyan military strongman Khalifa Haftar have arrested rival senior military official in the eastern city of Derna, held by jihadists since the 2011 armed uprising.

The spokesman for Haftar's self-styled Libyan National Army made the announcement in an online statement on Friday.

"The terrorist Yahya al-Osta Omar has been arrested in a special operation," the statement said.

"Omar is the security official in al-Qaeda and one of the most prominent leaders of the organisation," it added.

The LNA released an image of Omar, sitting handcuffed in civilian clothes.

The LNA launched an offensive on May 7 to "liberate" the coastal city, home to about 150,000 people and held by hardline fighters since the uprising that ousted dictator Muammar Gaddafi.

LNA forces have laid siege to Derna for nearly two years, making it difficult for residents to access humanitarian aid.

The city is held by a ragtag coalition of Islamist and jihadist militias, including groups close to al-Qaeda, hostile to both Haftar and the Islamic State group.

Some members of Haftar's forces have been implicated in war crimes, including Mahmud al-Werfalli, a commander of the al-Saiqa brigade based in Libya's second city of Benghazi.

The United Nations said on Friday it was alarmed by an increasing risk to civilians in the city.

"There have been increasing allegations that civilians have been arbitrarily detained, while others have been prevented from leaving the city," said Elizabeth Throssell, spokeswoman for the UN High Commissioner for Human Rights, in a statement.