DUBAI — With its campaign against Yemeni rebels at full throttle, Saudi Arabia has spared Al Qaeda which has capitalised on the chaos, but experts say Riyadh will have to hit them eventually.

Faced with the Shiite rebels' march on Aden, President Abed Rabbo Mansour Hadi's southern refuge, Riyadh assembled a Sunni-Arab coalition that launched a campaign of air strikes on March 26.

Since then, coalition warplanes have pounded Houthi positions and those of its allies across the country, as Sunni tribesmen joined the fight against the rebels.

"The growing confessional nature of the conflict definitely gives the extremists on both sides a bigger margin for manoeuvre, so fighting Al Qaeda might not seem like the most urgent priority," said Elie Al Hindy, political science professor at Notre Dame University in Lebanon.

This might explain why Riyadh did not react when Al Qaeda on April 2 seized Mukalla, the capital of Hadramawt province.

Experts have spoken of an adverse effect of the military intervention, evoking a "circumstantial alliance" between Riyadh and Al Qaeda, which considers Shiites to be heretics.

Saudi Arabia has been in war with Al Qaeda for more than a decade, hitting what it calls the "deviant group" with an iron fist.

"A de facto alliance can be ruled out," Hindy said.

Taking advantage of Hadramawt being generally spared the air raids, Al Qaeda in the Arabian Peninsula (AQAP) seized Mukalla airport and a military base full of heavy weaponry.

"While the coalition is busy with its job [striking Houthis], AQAP is benefiting from the situation by seizing positions," said Mathieu Guidere, Islamic studies professor at the University of Toulouse in France.

He argues that if the coalition succeeds in defeating the Houthis, "the next step will be to tackle AQAP which also threatens the legitimate authority in Yemen".

However, opening a second front now would complicate Riyadh's task, so key ally Washington is doing its share by pressing its campaign of drone attacks against the terrorists.

AQAP acknowledged this week that its ideologue Ibrahim Al Rubaish was killed in a drone attack near Mukalla.

And late on Saturday, three other militants died in the same manner in the southern province of Shabwa.

Since last year, Yemen’s government has been caught between the Houthi rebels in the north and Al Qaeda in the southeast.

But as the rebels allied with troops loyal to former president Ali Abdullah Saleh advanced on the south after seizing Sanaa, government forces collapsed and the president fled to Saudi Arabia.

According to Jean-Pierre Filiu of the Paris School of International Affairs, Riyadh is “hitting the wrong mark in taking Tehran and the Houthis as its main adversaries, rather than former president Saleh who is the main person responsible for Yemen’s descent into chaos”.

“The anti-Shiite mobilisation, rather than being anti-Saleh, plays into the jihadist hands,” he said.

Riyadh also needs to take into account the involvement of heavily armed tribes which are also fighting the Houthis.

Tribesmen seized the country’s only gas terminal at Balhaf last Tuesday, and tribal fighters three days later captured Masila oilfield in Hadramawt.

One tribal chief, Ahmed Bamaes, told AFP the tribesmen wanted to “protect” the facility to ensure it does not fall into the hands of Al Qaeda or the Houthis.

This takeover is a “another demonstration of the state collapsing and... a re-appropriation of resources confiscated by the regime of Saleh” during his three decades in power, said Filiu.

Military sources say current and former members of Al Qaeda are also fighting alongside Sunni tribesmen.

For Riyadh, not all jihadists are necessarily members of Al Qaeda, in that they belong to tribes that could be natural allies.

But any attempt to re-establish stability in Yemen will necessitate confronting Al Qaeda.

“Fighting Al Qaeda may not seem like the most urgent priority, but the eventual reinstatement of legitimate government is the right way to eradicate extremist factions,” Hindy said.

“But this will take time.”