Tamil Tiger rebels have launched deadly attacks on a breakaway faction they accuse of receiving military-backing.
Some of the wounded are at a government hospital in Polonnaruwa
A rebel spokesman told the BBC they had killed at least 10 members of the group headed by former Tiger rebel Col Karuna, suffering no losses themselves.
The Karuna group said it had lost five fighters, and recovered the bodies of seven Tiger rebels, in the raids on three of their camps in east Sri Lanka.
The latest violence puts further strain on a fragile ceasefire.
Tensions have been high after a Tiger bombing at a military compound and government air strikes on rebels.
The authorities deny accusations by the Liberation Tigers of Tamil Ealam (LTTE) that the Sri Lankan military supports the Karuna faction.
The early morning attack took place near the village of Welikanda in the eastern district of Batticaloa, 250km (150 miles) north-east of the capital, Colombo.
"We launched a limited operation against Karuna group to disarm them," the LTTE's local political leader, Daya Mohan, said.
"We killed over 10 of them and captured considerable amount of arms and ammunition. There is no casualty on the LTTE side."
The LTTE earlier said it had killed at least 15 renegade fighters. The Sri Lankan military said 10 Tigers had been killed.
Mr Mohan added: "The camp was in a government held area. It was situated between two Sri Lanka army camps. During the attack, the Sri Lanka army fired rockets against us."
However, Karuna spokesperson, Thooyavan, told the BBC Tamil service the camps were not in a government or LTTE-controlled area.
"The fight lasted for more than an hour," he said. "After the fight our [Karuna] strike force people recovered the bodies of seven LTTE cadres. Many more have been injured. From our side we lost five people."
Sri Lankan army spokesperson Brigadier Prasad Samarasinghe also denied the camps were in government areas, telling the BBC they were "in the jungles off Polannaruwa region in the LTTE-controlled territory".
The government also denied it fired mortar rockets at the LTTE fighters.
Col Karuna split from the LTTE in 2004, and the rebels say he is operating in government-controlled areas with Sri Lankan military support.
The Tigers want the group disarmed before they will hold talks with the Sri Lankan government on saving the ceasefire.
International mediators have been scrambling to save the truce, threatened by a fresh outbreak of violence this month.
Last Tuesday, a rebel suicide bomber killed at least 11 people at a military base in Colombo, triggering government air raids, which killed at least 12 people.
More than 60,000 people have been killed in Sri Lanka since the LTTE launched its campaign for a separate state in the north and east of the country in 1983.