* Islamists seize town south-west of recent fighting
* France says aims to deploy 2,500 troops in Mali
* Rebels say Mali will become next Afghanistan
* Concerned about reprisals, France tightens security
* U.N. Security Council meets Monday, EU to meet this week
By Bate Felix and Alexandria Sage
BAMAKO/PARIS, Jan 14 (Reuters) - Al Qaeda-linked Islamist rebels launched a counteroffensive in Mali on Monday after four days of French air strikes on their northern strongholds, seizing the central town of Diabaly and promising to drag France into a brutal Afghanistan-style war.
France, which has poured hundreds of troops into the capital Bamako in recent days, carried out more air strikes on Monday in the vast desert area seized last year by an Islamist alliance grouping al Qaeda's north African wing AQIM alongside Mali's home-grown MUJWA and Ansar Dine militant groups.
"France has opened the gates of hell for all the French," said Oumar Ould Hamaha, a spokesman for MUJWA, which has imposed strict sharia, Islamic law, in its northern fiefdom of Gao. "She has fallen into a trap which is much more dangerous than Iraq, Afghanistan or Somalia," he told Europe 1 radio.
Paris is determined to shatter Islamist domination of the north of its former colony, an area many fear could become a launchpad for terrorism attacks on the West and a base for coordination with al Qaeda in Yemen, Somalia and North Africa.
The French defence ministry said it aimed to deploy 2,500 soldiers in the West African state to bolster the Malian army and work with a force of 3,300 West African troops from the immediate region foreseen in a U.N.-backed intervention plan.
The United States, which has operated a counter-terrorism training programme in the region, said it was sharing information with French forces and considering providing logistics, surveillance and airlift capability.
"We have a responsibility to go after al Qaeda wherever they are," Defense Secretary Leon Panetta told reporters heading with him on a week-long tour of European capitals.
As French aircraft bombarded mobile columns of Islamist fighters, other fighters launched a counter-attack to the southwest of recent clashes, dislodging government forces from the town of Diabaly, just 350 km (220 miles) northeast of Bamako. French and Malian troops attempting to retake the town were battling Islamists shouting 'Allahu akbar', residents said.
The rebels infiltrated the town overnight from the porous border region with Mauritania, home to AQIM camps housing well-equipped and trained foreign fighters. A spokesman for Ansar Dine said its fighters took Diabaly, working with AQIM members.
Dozens of Islamist fighters died on Sunday when French rockets hit a fuel depot and a customs house being used as a headquarters. The U.N. said an estimated 30,000 people had fled the fighting, joining more than 200,000 already displaced.
France, which has repeatedly said it has abandoned its role as the policeman of its former African colonies, convened a U.N. Security Council meeting for Monday to discuss the Mali crisis.
The European Union announced it would hold an extraordinary meeting of its foreign ministers in Brussels this week to discuss speeding up a EU training mission to help the Malian army and other direct support for the Bamako government.
French Foreign Minister Laurent Fabius said France would do everything to ensure that regional African troops were deployed quickly to follow up on the French military action, which was launched to block a push southwards by the Islamist rebels.
"We knew that there would be a counter-attack in the west because that is where the most determined, the most organised and fanatical elements are," French Defence Minister Jean-Yves Le Drian told France's BFM TV.
France has said its sudden intervention on Friday, responding to an urgent appeal from Mali's president, stopped the Islamists from seizing the dusty capital of Bamako.
President Francois Hollande says Operation Serval - named after an African wildcat - is solely aimed at supporting the 15-nation West African bloc ECOWAS which received U.N. backing in December for a military intervention to dislodge the rebels.
Hollande's robust intervention has won plaudits from Western leaders and has also shot down domestic criticism which portrayed him as spineless and indecisive.
Under pressure from Paris, regional states have said they hope to send in their forces this week. Military chiefs from ECOWAS nations will meet in Bamako on Tuesday but regional powerhouse Nigeria, which is due to lead the mission, has cautioned that training and deploying troops will take time.
Two decades of peaceful elections had earned Mali a reputation as a bastion of democracy in turbulent West Africa but that image unravelled after a military coup in March left a power vacuum for MNLA Tuareg rebels to seize the desert north.
MUJWA, an AQIM splinter group drawing support from Arabs and other ethnic groups, took control of Gao, the main city of the north, from the Tuaregs in June, shocking Mali's liberal Muslim majority with amputation of hands for theft under sharia.
Malian Foreign Minister Tyeman Coulibaly said the situation had become "untenable" in the north. "Every day, we were hearing about feet and hands being cut off, girls being raped, cultural patrimony being looted," he told the French weekly Paris Match.
Last week's drive toward Bamako appeared to have been led by Ansar Dine, founded by renegade Tuareg separatist commander Iyad ag Ghali in his northern fiefdom of Kidal.
The group has said that the famed shrines of ancient desert trading town Timbuktu - a UNESCO world heritage site - were un-Islamic and idolatrous. Much of the area's religious heritage has now been destroyed, sparking international outrage.
France's intervention raises the threat for eight French hostages held by al Qaeda allies in the Sahara and for 30,000 French expatriates living in neighbouring, mostly Muslim states.
Concerned about reprisals at home, France has tightened security at public buildings and on public transport.
However, top anti-terrorist judge, Marc Trevidic, played down the imminence of the risk, telling French media: "They're not very organised right now ... It could be a counter attack later on after the defeat on the ground. It's often like that."
Military analysts warn that if French action was not followed up by a robust deployment of ECOWAS forces, with logistical and financial support from NATO, then the whole U.N.-mandated Mali mission was unlikely to succeed.
"The French action was an ad-hoc measure. It's going to be a mess for a while, it depends on how quickly everyone can come on board," said Hussein Solomon, a professor at the University of the Free State, South Africa.