A senior leader of Sri Lanka's Tamil Tiger rebels has been killed in a government air raid, the rebels say.
Mr Thamilselvan was the public face of the rebels
SP Thamilselvan was the head of the rebels' political wing and held an important position in their hierarchy.
The rebels said he died along with five others in an air strike by the Sri Lankan military on Friday morning.
Correspondents say the death will be a huge blow to the rebels. Fighting between troops and the Tamil Tigers has escalated in recent months.
The BBC's Roland Buerk in Colombo says Mr Thamilselvan was the public face of the rebels, meeting Norwegian peace envoys and giving interviews to the media.
The rebels' top leader, Velupillai Prabhakaran, has been in hiding for years.
Mr Thamilselvan's death could provoke an escalation in the civil war, our correspondent says. How the rebels choose to retaliate also remains to be seen.
The death of SP Thamilselvan follows that of another key rebel spokesman, Anton Balasingham, last year.
With both men dead it is not clear who would lead the Tigers in any negotiations in the future, although few anticipate moves towards peace now, our correspondent adds.
The Tamil Tigers announced the death of Mr Thamilselvan on their website on Friday.
The Tigers have suffered a series of recent reverses
"With deep sorrow we announce to the people of Tamil Eelam, the Tamil people living all over the world and the international community, that at 6am today, Friday 2 November 2007... head of our organisation's political wing Brig SP Thamilselvan was killed by the Sri Lankan air force aerial bombing," a statement said.
"With him Lt-Col Anpumani (Alex), Major Mihuthan, Capt Nethagy, Lieutenant Adchgivel and Lieutenant Vahaikumaran were also killed."
Later on Friday, it was announced that the rebels' police chief, P Nadesan, would replace Mr Thamilselvan. He will also remain in charge of police.
Reports say Mr Thamilselvan and his colleagues were killed by the pressure of the bomb blast which left their bodies otherwise unscathed.
The pro-rebel TamilNet website said the air strike was carried out in Kilinochchi, the rebels' northern stronghold.
Sri Lankan military spokesman Brig Udaya Nanayakkara said intelligence had confirmed that the head of the Tigers' political wing was dead.
He described the attack as a success and said the military had got rid of a leader who was at the top of the list.
It remains unclear how the military knew of Mr Thamilselvan's whereabouts.
Defence Secretary Gotabaya Rajapaksa, President Mahinda Rajapaksa's brother, warned rebel leaders to beware.
"This is just a message, that we know where their leaders are... if we want we can take them one by one," he told Reuters news agency.
Friday's air raid came after a Tamil Tiger attack on an Air Force base at Anuradhapura last week which left 14 security forces personnel dead and destroyed eight aircraft.
Observers say the two sides now seem to be gearing up for a major confrontation in the north of the country.
Paikiasothy Saravanamuthu of the Centre for Policy Alternatives think-tank said: "I think in any event we were going to see strikes and counter strikes after the Anuradhapura attack on the Air Force base.
"I think we will see more of that. That will be the pattern of the conflict into the future."
Despite losing territory in the east earlier this year, the rebels still control a vast swathe of land in the north.
A 2002 ceasefire which paved the way for inconclusive peace talks has existed on paper for more than a year.
The rebels are fighting for autonomy for minority Tamils in the north and east, claiming discrimination by the majority Sinhalese population.
About 70,000 people have died in more than 20 years of war. Thousands have fled their homes to escape recent fighting.