New Islamic State leader in Libya says group "stronger every day"

A senior Islamic State militant has said in an interview identifying him as the new leader of the jihadists' Libyan offshoot that the extremist organisation is getting "stronger every day" in the north African country.

Abdul Qadr al-Najdi, described in an interview released by the SITE monitoring group on Thursday as "the emir tasked with administering the Libyan provinces", said he was praying for Libya to be made the "vanguard of the Caliphate".

He also warned neighbouring countries that they would not be able to defend themselves from the militants.

"You are protecting yourself from the detonators with shields of bamboo, and from the flood with a ring of wood," he said, in the interview in the Islamic State publication al-Naba.

Tunisia, where more than 50 people died in an assault by Islamists near the Libyan border this week, has just completed a trench and barrier on its southern frontier in an effort to stop militants crossing.

Islamic State has taken advantage of the political chaos and security vacuum following the 2011 uprising that toppled Muammar Gaddafi to establish a presence in several cities. Western officials have expressed alarm over the expansion and estimates the number of its fighters to be as high as 6,000.

Last year it took full control of the eastern city of Sirte and the surrounding coastline. That had proved easier than expanding elsewhere in Libya, where "the number of factions and their disputes" was one reason for failure, Nadji said.

Islamic State militants were mostly pushed out of the eastern city of Derna by rival Islamist factions in June, and has been targeted by local security forces in the western city of Sabratha following a U.S. air strike on a suspected training camp in February.

Najdi described Islamic State in Libya as "still young" but said it was making progress in imposing religious law in areas under its control, in line with its actions in Iraq and Syria.

"The provinces of Libya have become the destination of the mujahideen and a sanctuary for the oppressed," he said.

"The numbers of immigrants multiplied from all areas despite the ardent attempts by the West to prevent their immigration."

Najdi said the Libyan province was "in constant communication" with central offices in Iraq and Syria, where the group took swathes of territory in 2014 but has since come under increasing pressure from air strikes and local forces.

A U.S. air strike in a suburb of Derna in November killed Islamic State's previous leader in Libya, known as Abu Nabil.