As France steps up its war on jihadists in Mali, there are concerns the intervention could trigger a wider conflict with al-Qaida -- just as the 2011 U.S.-NATO intervention in Libya that helped topple Moammar Gadhafi led to the Islamist conquest of northern Mali.

France "has opened the gates of hell," declared Omar Ould Hamaha, a leader of the Movement for Oneness and Jihad in West Africa, one of al-Qaida's allies in northern Mali.

"France ... has fallen into a trap much more dangerous than Iraq, Afghanistan or Somalia."

So far, after nearly a week of French airstrikes and ground action in what Paris calls Operation Serval, jihadist forces continue their advance southward, heading for Bamako, Mali's capital.

On Wednesday, they retaliated for the French operation when an estimated 20 fighters from an offshoot of al-Qaida in the Islamic Maghreb seized an internationally operated gas field in the Algerian desert and took dozens of foreigners hostage.

There are unconfirmed reports that some hostages, including an American and a Briton, have been slain.

That could draw their governments into the unfolding conflict in Mali, a remote African state that has become the center of a perceived strategic jihadist threat in the manner of Afghanistan, Iraq, Yemen and Somalia.

The attack on the Amenas gas facility threatened to drag Algeria, North Africa's military and economic powerhouse which has been sitting on the fence for months, into the fight.

But the big fear in the West is that al-Qaida and its allies will widen the battle under way in Mali by attacking across Africa and even in Europe.

U.S. Defense Secretary Leon Panetta branded the attack in Algeria a "terrorist act" and hinted at a possible military response by the Americans.

Algeria's still in the shadow of a civil war with Islamists throughout the 1990s and is still fighting the remnants, from which emerged AQIM, the main jihadist group in North Africa.

But even during that vicious conflict, the extremists did not target Algeria's oil and gas facilities, the country's economic lifeline.

The seizure of the Amenas field, operated by BP, Statoil of Norway and Algeria's state oil enterprise, was the first such attack in Algeria, underlining the jihadist threat across the complex region.

"The attack ... has raised fears of the conflict in Mali becoming an international battle bleeding across the porous borders of the Sahel and Sahara regions," Britain's Guardian newspaper observed

Lord Mark Malloch-Brown, a former U.N. deputy secretary-general and a former British government minister, warned the hostage-taking "is a brutal reminder of the perils of Western intervention.

"The French military operation in Mali ... seems to have tipped the world back toward a dangerous confrontation with radical Islam," he wrote in the Financial Times.

"While the hostage crisis and the vulnerability of the growing number of foreign-operated oil and gas facilities across Africa seem likely to bring early rain on the French parade, the real dangers lie ahead.

"The loosely networked al-Qaida brand will avoid pitched battles with the French and melt back into the desert, as the Taliban did in Afghanistan, regroup and begin an insurgency against a logistically stretched occupier, mounting attacks not just in Mali but back home in France...

"The French have given refreshingly firm leadership to a needed intervention but as the stand-off around the Algerian gas field shows, it's already starting to get harder."

African states, jolted by the jihadist thrust, have pledged to send troops to aid the French, and the European Union is set to back France and send military advisers to train African forces.

Algeria, Mali's northern neighbor and a former French colony, has allowed French aircraft to use its air space even though Algiers favors a negotiated settlement and is reluctant to allow foreign forces on its territory.

Washington doesn't want to get involved in another war after Afghanistan and Iraq, but it's pledged intelligence backup and is mulling logistical support as well.

"Over and over, Western intervention ends up -- whether by ineptitude or design -- sowing the seeds of further intervention," observed U.S. anti-war activist Glenn Greenwald.

Casting a baleful eye over the intervention in Libya, a country still ravaged by internal postwar conflicts, he noted: "Nobody is better at creating its own enemies, and thus ensuring a posture of endless war, than the U.S. and its allies."