"There were eight suspects (who) escaped. This is what they (prison officials) have told us," Nihal Karunaratne, senior police official for the eastern district of Batticaloa, told The Associated Press.
"This has to be an inside job," Karunaratne said.
He said the suspects broke out after being freed from their jail cells to bathe in the morning.
Police were searching for the eight, and for evidence that prison officials helped them flee, he said. No other details were immediately available.
The Tamil Tigers have fought a civil war against the Sri Lankan government since 1983 to create a separate state for ethnic minority Tamils, accusing the majority Sinhalese-dominated state of discrimination.
More than 65,000 people were killed in the conflict before a 2002 Norway-brokered cease-fire, which has come under heavy strain in recent months due to escalating violence.