KANO, Nigeria -- Security forces fired shots and tear gas Monday to disperse youths baying for revenge after bloody riots that claimed 18 lives sparked by a Muslim rally against U.S.-led reprisal attacks on Afghanistan.

"Tension is still high in Sabon Gari and nearby Galadima districts of the city, and security agents are still firing shots and tear gas in the air to scare a group of about 300 street urchins shouting revenge slogans," a resident said in this northern Nigerian city.

Although the palpable tension has not degenerated into violence, rumors of fresh unrest in some parts of the city continued to spread.

"On each occasion we heard the rumor, we dispatched our men there and so far they have not seen any evidence of a fresh outbreak of violence in any part of Kano city," a top police officer told AFP.

No new violence broke out in the city on Monday.

In Galadima district, where about 50 shops belonging mostly to Muslim traders were burned, hundreds of youths gathered early Monday shouting "Ramuwa" ("revenge" in Hausa, the main language in northern Nigeria).

The shops were set ablaze after they were looted.

The youths accused Christian traders from southern Nigeria of carrying out the destruction and looting and threatened revenge by invading a market where the Christian traders operate.

Kano, northern Nigeria's largest city, is mainly Muslim and has been a hotbed of religious unrest in the past two decades.