The authorities in Nigeria's southeastern Anambra state have imposed a curfew, following days of violence involving a separatist group and the police.

Governor Peter Obi of Anambra state, in a televised address Sunday, announced the introduction of a curfew and the deployment of soldiers in the market city of Onitsha to stop four days of violence.

Mike Mbonye, a journalist in Onitsha, said the curfew would last until Saturday, while more troops are being sent to the city to deal with the unrest. He said President Olusegun Obasanjo authorized the security measures.

"President Obasanjo has given him the approval to put in place all necessary security measures and actions that will guarantee and ensure safety of lives and property in Onitsha," said Mike Mbonye. "Also, he confirmed that there is now a joint army and police patrol in Onitsha."

A police raid on Thursday led to clashes with the separatist group, Movement for the Actualization of the Sovereign State of Biafra, known as MASSOB.

At least six people were killed in the clashes, which continued into Saturday, prompting the authorities to bring in soldiers to try to deal with the crisis.

Mbonye says the state government acknowledges that the police can no longer cope with the violence.

"The security situation in Onitsha is beyond the scope of the Nigerian police, hence he, the governor, wrote to the presidency, and President Obasanjo approved the deployment of the army to assist the police patrol the streets of Onitsha," he said.

MASSOB, whose leader, Ralph Uwazuruike is in jail facing a treason trial, emerged in the early 1990s to campaign for the peaceful secession of southeastern Nigeria, a region dominated by the ethnic Ibo group. Some MASSOB members have been involved in fighting in the past.

An attempt by the Ibos to beak away and form a separate Biafra state led to a bitter three-year civil war in 1967, culminating in a decisive victory for federal troops.

The Ibos have alleged widespread victimization and neglect since the end of the secession attempt, and most Ibos still nurse the hope of a separate Biafra state.

MASSOB enjoys a lot of support among Ibos, and the crackdown by the authorities is seen as an effort to check the group's growing influence in the region. The police have conducted several raids on suspected MASSOB hideouts.

Onitsha residents say some powerful local politicians are also seeking to weaken the group ahead of general elections. The local transport union clashed with MASSOB in recent days, and some people suspect a link to a wealthy politician.

Hundreds of MASSOB's members have been arrested, while the group's leader remains in jail, pending trial.