BENGHAZI, Libya (Reuters) - Authorities in eastern Libya say they have arrested a woman believed to be the wife of veteran Algerian jihadist Mokhtar Belmokhtar after she traveled from southern Libya to the city of Derna to give birth.

East Libya’s counter-terrorism department said the woman, named as Tunisian Asma Kadoussi, had told investigators that Belmokhtar was alive and living in southern Libya.

A spokesman for the department, Sami al-Matrih, told Reuters on Monday that Kadoussi had given birth to a girl 40 days ago.

Belmokhtar, leader of the al-Mourabitoun group, has long been a major militant figure in the Sahel with deep connections across the region. He has repeatedly been pronounced dead by authorities before resurfacing to plot attacks or kidnappings, including a raid on an Algerian gas plant that killed 40 workers in 2013.

In June 2015, Belmokhtar was targeted by a U.S. air strike in the eastern Libyan city of Ajdabiya, but his group declared shortly afterwards that he had survived.

The east Libyan counter-terrorism office said in a statement that Kadoussi had been traveling with a second Tunisian woman, Afaf Haji, and that the two had stayed with an al Qaeda militant in Derna named as Jibril al-Abd.

They were detained on a road south of Derna after hospital staff in the city tipped off authorities because a foreign woman had checked in to give birth without her husband, the statement said.

According to initial investigations the two women had earlier been staying in “terrorist camps” in the central Libyan desert region of Jufra with Belmokhtar, and the statement said that “it was him who sent them to Derna for the birth”.

Authorities posted photos of Tunisian identity cards and forged Libyan passports that they said the women were carrying.

Derna has historically been a stronghold for Libyan Islamists, and Islamic State took control of the city in 2014 before being ousted by rival Islamists and other opponents.

The city, about 250 km (155 miles) east of Benghazi, is now the scene of fighting between security forces loyal to Libya’s eastern government and an Islamist-led alliance.

Militants loyal to both al Qaeda and Islamic State have a presence in the vast expanses of Libya’s southern desert, an increasingly lawless space due to the conflict that developed after Libya’s 2011 revolution.

Now in his 40s, Belmokhtar fought in Afghanistan in the 1980s before joining the Islamic Armed Group (GIA) during the Islamist insurgency in Algeria in the 1990s. He then helped found the Salafist Group for Call and Combat (GSPC), which later transformed into al Qaeda’s North African wing.

As well as the 2013 gas plant attack in In Amenas, which authorities said was planned from Libya, Belmokhtar has been blamed for kidnapping foreigners and running lucrative smuggling rings in the Sahara.