A suspected suicide bomber has killed a top Sri Lankan general and three other people near the capital, Colombo.
The blast hit a car carrying Maj Gen Parami Kulatunga near a military base just outside the city, officials said.
Gen Kulatunga was the third-highest ranking officer in the Sri Lankan army and a veteran of the civil war.
Tamil Tiger rebels have been blamed for the attack but they deny involvement. Violence between the two sides has claimed almost 700 lives this year.
The BBC's Dumeetha Luthra in Colombo says that the latest attack further raises fears that Sri Lanka is heading towards war.
Gen Kulatunga was travelling to the military base in the town of Panipitiya, about 20km (12 miles) east of Colombo when a suicide bomber rammed his motorcycle into his car, the military said.
Witnesses said the blast shook the town and produced billowing smoke. The general's car was completely destroyed.
"There was a sudden noise and we could see fire from the other side [of the road]," an eyewitness, Keneth Guruge, told the BBC.
"When we came here to see what happened we saw an army casualty bleeding badly."
Two soldiers, a civilian and the suspected bomber were also killed in the blast, the military said. A number of others were injured.
President Mahinda Rajapakse said the Liberation Tigers of Tamil Eelam, as the rebels are called, were ignoring appeals for peace.
"These killings are further examples of the LTTE's concerted efforts to derail the peace process through acts of terror," the president said in a statement.
Army spokesman Prasad Samarasinghe told the BBC the blast was a direct ceasefire violation.
"When you consider the past, all these suicide bomb attacks in Sri Lanka were conducted by [rebel] suicide cadres. So there's nothing more to prove," he said.
Jun 06: Gen Parami Kulatunga killed in attack on his convoy
Jun 06: More than 60 killed in a bomb attack on a passenger bus
Apr 06: Army chief Sanath Fonseka seriously injured in attack on his HQ
Aug 05: Foreign Minister Lakshman Kadirgamar shot dead in his house
Jul 01: Attack on Colombo airport kills 18 and destroys planes
Dec 99: President Kumaratunga wounded in failed assassination attempt
A rebel spokesman, Seebaratanam Puleedevan, denied any involvement in Monday's blast. "The Sri Lankan army spokesperson is always very quick to blame [the rebels]," he told the BBC.
The rebels routinely deny carrying out such attacks, often claiming they are the work of ordinary Tamil civilians reacting to state oppression.
About 700 people have been killed since the beginning of the year, many of them civilians and members of the security forces.
Many Tamil civilians have also been killed over that time - by the security forces or affiliated paramilitary units, the rebels allege. Others blame some of those deaths on the rebels or other armed groups.
In April, a suicide bomb attack in Colombo nearly killed the army chief Lt Gen Sarath Fonseka.
The military blamed the rebels for the attack and launched air strikes on their positions in the east.
Last week, the rebels extended a deadline for European Union (EU) ceasefire observers to withdraw from the country.
They had originally given the EU monitors a month to leave, after the EU listed the Tigers as a terrorist organisation at the start of June.