COLOMBO, Aug. 20 (Xinhua) -- At least 11 people were injured when a massive clash erupted in the female ward of Colombo's main prison on Monday.

The incident occurred as a group of inmates, who were allegedly involved in drug trafficking, were protesting against their transfer to other prisons in the island country.

A prison spokesperson from the Welikada Prison told Xinhua that security had been heightened at Welikada and other prisons throughout the island country after the female inmates revolted during the protest which was held on top of the prison roof.

The spokesperson said the protest began on Monday morning.

Following the clash, 52 female inmates had been transferred to other prisons.

"We humbly requested them to stop their protest but the inmates then attempted to run towards the prison gates following which officers tried to prevent them. The injured officers and inmates have been admitted to a hospital," the spokesperson said.

The police said the situation in the prison remained tense and additional security had been deployed.