The death toll in an explosion targeting Tunisia’s presidential guard has risen to 13 and the perpetrators remain unidentified, the interior ministry said.
Another body was discovered in the charred remains of a bus carrying presidential guards that exploded in central Tunis, spokesman Walid Louguini said.
Mr Louguini could not confirm or deny Tunisian reports that the body could be that of a suicide bomber who jumped on to the bus just before the bomb exploded.
Troops fanned out around the capital and President Beji Caid Essebsi declared a month-long state of emergency after Tuesday’s attack.
The blast rattled the North African country after two major attacks by Islamic extremists that targeted tourist sites earlier this year.
Radical gunmen staged two attacks in the country earlier this year that killed 60 people, devastated the tourism industry and rattled this young democracy.
No-one immediately claimed responsibility for the attack against the presidential guard, an elite security force that protects only the president.
Mr Essebsi, who was not on the bus at the time, convened an emergency meeting of his security council. Speaking on national television, he said Tunisia is at “war against terrorism”.
He urged international co-operation against extremists who have killed hundreds around Europe and the Middle East in recent weeks, from Paris to Beirut to a Russian plane shot down over Egypt.
“I want to reassure the Tunisian people that we will vanquish terrorism,” he said.
Witness Bassem Trifi, a human rights lawyer, said the explosion hit the driver’s side of the bus, describing a “catastrophic” scene.
“I saw at least five corpses on the ground,” he said. “This was not an ordinary explosion.”
The attack came days after authorities visibly increased the security level in the capital and deployed security forces in unusually high numbers.
US Secretary of State John Kerry, visiting Tunis earlier this month, pledged expanded economic and security support for Tunisia, whose popular uprising unleashed the democracy movements across the region in 2011 that became known as the Arab Spring.