Sri Lanka's main opposition party has described the deaths of 27 inmates after a prison riot as a "cold-blooded massacre" and demanded a parliamentary investigation into the incident.
Authorities have said the prisoners died in a shootout.
But Mangala Samaraweera, an MP for the United National party, said that he had information that most of the prisoners killed during Friday's clash had been gunned down by police commandos and soldiers.
"It's a massacre that has to be condemned. It shows the breakdown of the rule of law in the country," Samaraweera said.
"Information I have is that most of the prisoners were cold-bloodedly gunned down."
He said the party has called for a parliamentary committee to be appointed to investigate.
Officials have said the clash erupted when prisoners attacked a search team that went into the Welikada Prison facility in Colombo looking for narcotics and communication devices.
The prisoners armed themselves by breaking into the armoury, they said.
On Friday night, the prisoners were seen holding up assault rifles from the rooftop and throwing rocks at officials.
Forty-two other people, including police commandos and soldiers, were wounded in the clashes.