GAO: France has bombed a rebel hideout in northern Mali’s largest city, intensifying a security lock-down against guerrilla attacks as the French-led campaign entered its second month.

Al Qaeda in the Arabian Peninsula has called for jihad against France in Mali, a monitoring group said on Tuesday, after four days of suicide attacks and guerrilla fighting in territory French-led forces reclaimed from rebels.

The call to holy war from AQAP, the global network’s Yemen-based branch — which US officials have labelled Al Qaeda’s most dangerous franchise — came as troops sought to tighten a security lock-down in Gao, the largest city in northern Mali and the target of a string of Islamist attacks.

AQAP condemned France’s month-old military intervention against Islamist groups in the partially desert nation as a “crusader campaign against Islam,” and called on Muslims everywhere to join the fight against it, the SITE Intelligence agency said.

“Supporting the Muslims in Mali is a duty for every capable Muslim with life and money, everyone according to their ability,” AQAP’s Sharia Committee said in a statement reported by US-based SITE, which monitors extremist Internet forums.

It said jihad is “more obligatory on the people who are closer” to the fight and that “helping the disbelievers against Muslims in any form is apostasy.”

The statements were an apparent reference to north African countries, notably Algeria, where Islamist gunmen attacked a gas field after the government agreed to let French warplanes use Algerian airspace, unleashing a hostage crisis that left 37 foreigners dead.

France launched its operation in Mali on Jan. 11, after the interim government requested help against Islamist insurgents who had seized the north for 10 months and were advancing into southern territory.

Paris sent in fighter jets, attack helicopters and 4,000 troops, racking up a string of early successes as French and African soldiers drove the extremists from Gao, Timbuktu and the rest of the towns under their control.

But the Islamists have now started a campaign of suicide attacks, landmine explosions and guerrilla fighting — a troubling turn for France, which is eager to wind down the operation in its former colony and hand over to United Nations peacekeepers.

Troops from Mali and Niger patrolled the streets of Gao on Tuesday making periodic arrests, after four days of violence that began with back-to-back suicide bombings and an attack on the city centre by fighters from the Movement for Oneness and Jihad in West Africa (MUJAO).

Malian Defence Minister Yamoussa Camara said three Islamists had been killed in the fighting on Sunday and 11 captured.

Three Malian soldiers were slightly wounded, he said.

Except for the heavy patrols, central Gao was nearly deserted on Tuesday.

“People are afraid because of the security situation and because we’re making arrests,” said a Malian officer.

Security forces continue to discover stockpiles of explosives and ammunition throughout Gao every day, a Malian military source said.

Paris announced last week it wanted some 8,000 African troops slowly being deployed to be incorporated into a UN peacekeeping mission.

But UN Deputy Secretary-General Jan Eliasson said on Monday “there is still hesitation from the government of Mali.”

In any case, he added, the situation on the ground would first have to be more stable and any UN peacekeeping force there would require a UN resolution.