Nigeria is said to have opened ceasefire talks with with the shadowy Islamic sect Boko Haram, blamed for hundreds of deaths in bombings and shootings over the past 18 months.

Political and diplomatic sources, speaking on condition of anonymity, say intermediaries are bringing messages between the government and militant leaders.

Reports from Nigeria say Boko Haram has called for all of its detained members to be released from jail as a condition for a ceasefire. The government is considering the proposal.

President Goodluck Jonathan is under mounting pressure to restore security in the north, where Boko Haram has carried out scores of attacks, many targeting police, government officials and other authority figures.

In an effort to stem the crisis, Mr. Jonathan recently declared a state of emergency in 15 areas and deployed extra troops to the north. But attacks have continued.

Boko Haram has refused the president's earlier offers to open talks, citing what it says is the military build-up in northern states.

The stalemate has led not only to divisions between military and civilian leaders and set off political infighting among those competing to influence President Jonathan.

Much about Boko Haram remains unknown, but it is believed to want wider implementation of sharia, or Islamic law.

Boko Haram first came to international attention with a brief but violent uprising against the government in July 2009. The uprising sparked a heavy military response and a week of fighting that killed some 700 people.