COLOMBO: At least nine people were killed and another 26 wounded at Sri Lanka's main prison on Friday after inmates overpowered guards and fought gun battles with elite police commandos, officials said.

Clashes erupted as elite police Special Task Force (STF) commandos carried out a search inside the Welikada prison for drugs and smuggled mobile phones, a military official at the scene told AFP.

“Some of the inmates grabbed weapons and have used them,” the officer said asking not to be named.

“We have ringed the prison and closed the adjoining Base Line road to make sure civilians don't get hit by gunfire.”

Colombo National Hospital director Anil Jasinghe said nine people were dead on admission.

“A total of 35 people were brought in and nine of them were already dead,” Jasinghe told reporters.

“Six people are in a critical condition.”The identity of the victims was not immediately clear, but witnesses said the dead appeared to be inmates. Some of the inmates got onto a roof and fired at troops and police on the ground.

Police and troops fired back, witnesses said. Jasinghe said a police deputy was among those brought in for treatment.

Troops used armoured vehicles to move in reinforcements as inmates kept on firing, witnesses said.

There was similar violence at the same penitentiary in January when 25 inmates and four guards were wounded.

In 2010, more than 50 police and prison guards were wounded in a riot during another raid to seize illegal mobile phones.