At least 80 people have been killed since Monday in clashes in two northern Nigerian cities triggered by Islamists waging an insurgency against the government, figures from police and the Red Cross showed today.

Boko Haram insurgents waged gun battles with security forces in the remote northeastern city of Damaturu, near the radical sect's heartland, throughout yesterday, police chief for the surrounding Yobe state Patrick Egbuniwe told Reuters.

He said 40 people were killed, 34 insurgents and 6 security forces.

In separate clashes between Muslim and Christian residents of the northern city of Kaduna yesterday, triggered by suspected Islamist bombings of three churches two days earlier, at least 40 people were killed and 62 wounded, according to figures from local Nigeria Red Cross official Awwal Sani.

The escalating violence has raised fears of wider sectarian conflict in a country reeling from months of attacks on churches, government buildings and other sites by the Boko Haram sect.

The movement styled on the Taliban appears bent on provoking Christian-Muslim clashes as part of its campaign to carve an Islamic state out of parts of Nigeria.

Pope Benedict today appealed for an immediate end to what he called "terrorist attacks" against Christians in Nigeria and urged all sides to avoid reprisals.

"I am following with deep concern the news from Nigeria, where terrorist attacks are continuing especially against Christians," the pope said at his weekly general audience.

"I appeal to those responsible for the violence to immediately stop the spilling of the blood of many innocents."He urged all groups in Nigeria to shun "the path of vendetta" and work towards building a peaceful society where people were free to practise their religion," he added.