PESHAWAR, Pakistan (AFP) - Suspected militants on a motorbike threw grenades at a mosque in the north-western Pakistani city of Peshawar, killing at least three Islamic preachers and wounding 18 others, officials said on Friday.

The attack happened on the outskirts of Peshawar, the gateway to Pakistan's troubled tribal regions where security forces have been battling Taleban and Al-Qaeda linked militants.

"Two attackers came on a motorbike and hurled grenades at a mosque soon after a preaching group arrived there late on Thursday night," senior police official Rahim Shah told AFP.

"At least three people were killed and 18 others got wounded. Two of them are serious," he said.

He said that a group of 25 preachers had arrived in the area to organise Islamic teaching sessions.

Many Pakistanis go on preaching missions in and outside the country to promote Islamic teachings among muslims and non-muslims. They travel in groups and stay at mosques for several days.

Another police official said that the attackers came from the semi-autonomous tribal region.

"They came from Khyber tribal district and fled towards that area after the attack," another police official Muhammad Ali told AFP.

Pakistan says more than 40,000 people have been killed in attacks by Al-Qaeda and Taleban-led militants in the last decade.

Washington considers the tribal belt as the main hub of Taleban and Al-Qaeda militants plotting attacks on the West and in Afghanistan.