Nigerian police dispatched special forces to the northwestern state of Zamfara after a weekend attack that may have killed more than 200 people.

The forces include a counter-terrorism unit, intelligence personnel and airborne surveillance, police spokesman Frank Mba said late yesterday in an e-mailed statement. Gunmen killed more than 200 people in Maru local government area, 85 kilometers (53 miles) south of the state capital, Gusau, Lagos-based ThisDay newspaper reported today. About 150 of the victims were buried in a mass grave, it said.

The violence was “the latest in a series of deadly raids by armed bandits and suspected cattle rustlers on communities in the state in the past two years,” Poole, U.K.-based risk consultancy Drum Cussac said today in e-mailed comments.

With less than a year before general elections, Nigerian security forces are increasingly stretched in their efforts to quell violence and lawlessness across huge swathes of the country, Africa’s biggest economy and its top oil producer.

In northeastern Nigeria, the army has been fighting the Islamist militant group Boko Haram for four years in a conflict that Brussels-based International Crisis Group said this month has killed more than 4,000 people and forced almost half a million to flee their homes.

President Goodluck Jonathan declared a state of emergency in three northeastern states in May to fight Boko Haram, which means “western education is a sin” and is has carried out a violent campaign to impose Shariah, or Islamic law, in the country.

Last month the army started operations against “criminal gangs” in the central states of Benue, Plateau and Nasarawa, which borders the Federal Capital Territory, home to the capital, Abuja, after clashes between mainly Muslim farmers and predominately Christian farmers.