The UN Security Council has said it is not ready to back a West African intervention force in northern Mali, which has been seized by Islamist militant groups. The council condemned the destruction of ancient shrines in the historic city of Timbuktu, saying it could constitute a war crime. The West African bloc, Ecowas, wants to send 3,000 troops to Mali. But a UN diplomat told the BBC that the council wanted more details. "Before endorsing an Ecowas force, we would need a clearer plan, more information about what the objectives are, and more evidence that such a force would have a reasonable chance of meeting those objectives," he said. Mali's neighbours have lobbied for the UN to back their proposed force, fearing the spread of Islamist militancy from northern Mali. Thursday's UN Security Council resolution also warned that "attacks against buildings dedicated to religion or historic monuments can constitute violations of international law". This means that a case could be referred to the International Criminal Court (ICC) in The Hague, whose prosecutor has already condemned the recent destruction of Muslim tombs in Timbuktu as "war crimes". 'No to imported Islam' The Ansar Dine group, which is said to have links to al-Qaeda, seized control of Timbuktu earlier this year and said it destroyed several of the city's shrines as they contravened its strict interpretation of Islam. Ansar Dine spokesman Sanda Ould Bamana told the BBC that Islamic law did not allow the building of tombs taller than 15cm (6in). The UN cultural agency Unesco and Mali's government have called on Ansar Dine to halt its campaign. Unesco has also expressed concern that valuable artefacts and manuscripts may be smuggled out of the region and has urged neighbouring countries to prevent this. Timbuktu owes its international fame to its role as a centre of Islamic learning, based in its three large mosques, in the 15th and 16th Centuries. It is also known as the "city of 333 saints", which originate in the Sufi tradition of Islam. Ansar Dine's Salafist beliefs condemn the veneration of saints. The group seized control of Timbuktu in April, after a coup left Mali's army in disarray. Initially, it was working with secular ethnic Tuareg rebels demanding independence for northern Mali's desert territories but the groups have recently clashed and Islamist forces are in control of northern Mali's three main centres - Timbuktu, Gao and Kidal. On Thursday, there was a further demonstration in Mali, including some religious leaders, against the northern rebellion in the capital, Bamako. "No to imported Islam, yes to the Islam of our parents," read one banner, AFP news agency reports. The day before, some 2,000 - mainly northerners - gathered in central Bamako to protest against Islamist occupation, calling for arms to allow them to go and fight the militants. Meanwhile, Ecowas's mediation efforts have been dealt a further blow by the decision of the interim President Dioncounda Traore not to attend talks in Burkina Faso over the weekend. Under pressure from Ecowas, the coup leaders handed over power to Mr Traore after the putsch, but he was beaten unconscious by protesters in May and remains in France wHere he went for medical treatment.