KARACHI, Pakistan, Dec. 1 -- Clashes between two ethnic groups in Pakistan's port city of Karachi during the weekend killed at least 28 people, police said Monday.

The groups, which were not identified, rioted, attacked each other and indulged in arson in several sections of the city, the English-language newspaper Dawn reported, adding more than 50 shops and at least 60 vehicles were set on fire.

Authorities in Sindh province, of which Karachi is the capital, banned riding on two-wheeled vehicles for three days to curb sniping, Dawn said.

Karachi Police Chief Waseem Ahmed told the newspaper 28 people had been killed and more than 150 people injured. He said at least 100 people had been arrested and police had seized weapons from them.

About 800 paramilitary troops were deployed in the city to assist police, the newspaper reported.

Separately in Pakistan's violence-wracked northwest region, five people were killed and 25 others injured Monday when a suspected suicide bomber blew himself up at a security force check-post near Sangota in the scenic Swat valley, Geo TV reported quoting the local authorities.

Other reports put the death toll at eight.(UPI)