West African leaders met at an emergency summit Sunday to plot a military strategy to wrest control of northern Mali from Islamist groups as fears grow over the risks the extremists pose to the region and beyond.

Leaders from the 15-nation Economic Community of West African States gathered in the Nigerian capital Abuja to approve a military blueprint that will eventually be sent via the African Union to the UN Security Council for review.

"Maximum pressure must be maintained with a strengthened military intervention plan," UN special representative for West Africa Said Djinnit said ahead of the summit's opening.

"Everybody wants a military intervention that targets only the terrorists... Our preferred option remains dialogue."

Mali rapidly imploded after a coup in Bamako in March allowed Tuareg desert nomads, who had relaunched a decades-old rebellion for independence, to seize the main towns in the desert north with the help of Islamist allies.

The secular separatists were quickly sidelined by the Islamists, who had little interest in their aspirations for an independent homeland and set about implementing their version of strict sharia law, meting out punishments including stonings and destroying World Heritage shrines.

Discussions among West African states so far have involved the deployment of more than 3,000 troops from the region to Mali, with more contributions to be requested from other countries. An ECOWAS source has said military chiefs were requesting a total of 5,500 troops.

Regional leaders have stressed that dialogue remains the preferred option to resolve the crisis in what was once one of West Africa's most stable democracies, but they have also warned that talks are not open-ended.

Representatives from countries outside ECOWAS were also invited to Sunday's summit, including from Mauritania and Algeria, which neighbour Mali, as well as South Africa and Morocco, which currently hold seats on the UN Security Council.

Mauritania was represented by Foreign Minister Hamady Ould Hamady, while Algeria sent its minister in charge of African affairs, Abdelkader Messahel. Libya was also represented, an ECOWAS spokesman said.

Security was tight at the summit venue, with mobile phone networks inaccessible from inside as heads of state arrived.

ECOWAS Commission President Kadre Desire Ouedraogo has said the bloc should pursue a dual approach of dialogue and military pressure.

The UN special envoy for the Sahel, Romano Prodi, a former prime minister of Italy and ex-president of the European Commission, has said every effort would be made to avoid military intervention.

But some analysts have questioned whether a negotiated solution is possible with Islamist extremists intent on establishing a theocratic state.

"There's a sense in which (military force) is the only course open, because clearly there's nothing to negotiate," said Jibrin Ibrahim, head of the Nigeria-based Centre for Democracy and Development.

At the same time, analysts and others warn of the risks a continued occupation of the north poses to countries beyond Mali. They say it could provide a safe haven to Al Qaeda-linked extremists and criminal groups.

The ECOWAS military strategy the leaders were examining Sunday was drawn up with the help of experts from the European Union, the African Union, United Nations and the region, which is also seeking logistical support from elsewhere.

Foreign and defence ministers from five European countries -- France, Germany, Italy, Poland and Spain -- are expected to meet next Thursday to discuss a European mission to train Malian troops.

Algeria, seen as important to any military operation, has been hesitant to get involved, preferring a negotiated solution.

While not a member of ECOWAS, Algeria is viewed as key due to its superior military capabilities, intelligence services and experience battling Islamist extremism, along with the long border it shares with Mali.