Libya Dawn fighters fire an artillery cannon at ISIS militants near Sirte, March 19.

TRIPOLI — “Islamic State” militants have effectively taken over former dictator Muammar Gaddafi’s home city of Sirte as they exploit a civil war between two rival governments to expand in North Africa.

Libya, which has descended into near anarchy since NATO warplanes helped rebels overthrow Gaddafi in a 2011 civil war, is now the third big stronghold for the extremist group, which declared a Caliphate to rule over all Muslims from territory it holds in Syria and Iraq.

ISIS fighters became a major force last year in Derna, a jihadi bastion in Libya’s east, and quickly spread to the biggest eastern city Benghazi, where they have conducted suicide bombings on streets divided among armed factions.

By occupying Sirte over the past four months they have claimed a major city in the center of the country, astride the coastal highway that links the east and west.

They made their presence known to the world in February by kidnapping and beheading more than 20 Egyptian Christian oil workers on a beach and posting video on the Internet.

In Libya, the group deploys locally-recruited fighters, led by envoys sent from Syria and Iraq. Those include Libyans returned from fighting on Syrian and Iraqi frontlines.

Their gains in Libya, just across the sea from Italy, are worrying European governments and north African neighbors. But so far Western countries, which are bombing ISIS positions in Syria and Iraq, have steered clear of that sort of intervention in Libya.