Sri Lanka's military is carrying out air strikes on suspected Tamil Tiger rebel bases for a second day, after a suicide attack on army headquarters.
At least eight people were killed in the attack on army headquarters
Army chief Lt Gen Sarath Fonseka was seriously injured in Tuesday's blast, which killed at least eight people.
The strikes are the first official military action since a 2002 ceasefire.
The rebels have warned of retaliation if strikes continue and have asked if Colombo has declared war. They say at least 11 people have been killed.
Some 3,000 families had been displaced from their homes following the military attack, rebel official S Elilan told the Associated Press agency.
As well as the dead, many more people could be buried in the rubble of damaged buildings, he said.
"There are many people urgently needed medical attention but we can't transport them because the roads are closed," the agency quoted him as saying.
The military said air and naval attacks had resumed on Tamil Tiger bases around Trincomalee port in the north-east of the country, after its navy ships were attacked.
It said three civilians had been killed and at least 11 people injured - including two navy sailors - in rebel attacks overnight.
President Mahinda Rajapakse said he did not want a return to conflict but would not be cowed by bomb attacks.
"I emphasise and caution that one should avoid mistaking our desire for peace and our responsibility to achieve it as a government, as weakness," he said in a televised address following Tuesday's suicide bombing.
But rebel spokesman S Puleedevan told Reuters news agency on Wednesday it was "like a war situation in Trincomalee".
Helen Olafsdottir, spokeswoman for the European team monitoring the ceasefire, said the government had closed a road providing the only land link between the south of the country and the rebel-held areas in the north, AP reported.
Escalating violence in the north and east of the country over the past three weeks has targeted Sri Lanka's security forces on a regular basis.
About 100 people have died, some 70 of them soldiers.
The BBC's Dumeetha Luthra in Colombo says some government officials have said privately the president is under immense pressure from the military to continue the air strikes.
Rebel official S Elilan has asked the Sri Lankan Monitoring Mission to "clarify" whether the military had launched a "full-scale war violating the ceasefire agreement", according to Tamilnet.
August 2005: Foreign Minister Lakshman Kadirgamar shot dead at his home
July 2004: Woman suicide bomber tries to kill government minister
July 2001: 18 people killed and planes destroyed in attack on Colombo airport
He said the strikes were unprovoked.
The rebels have also denied being behind recent bomb attacks, although police say the explosion at the army headquarters in Colombo bears all the hallmarks of the Tigers.
A woman who made herself appear heavily pregnant to conceal the explosives is believed to have carried out the attack.
The attack is believed to have been aimed at Lt Gen Fonseka, who was seriously injured along with 27 other people.
This was the first suicide bombing in the Sri Lankan capital since July 2004, and the most serious blamed on the Tamil Tigers since they signed a truce with the government in 2002.
The Tigers began their armed campaign for a separate homeland for the island's Tamil minority in the 1970s.
Efforts are continuing to persuade the rebels to return to peace talks in Switzerland. Last week they pulled out of negotiations, accusing the government of attacks on ethnic Tamil civilians.