A day of national mourning has been held in Lebanon amid opposition protests over a massive car bombing a day earlier in Beirut.
The dead included internal intelligence chief Wissam al-Hassan, who was close to the anti-Syrian opposition.
Protesters have been blocking roads in Beirut and other cities. The opposition blames Damascus for Friday's attack.
PM Najib Mikati offered to resign, but President Michel Suleiman has asked him to stay on in the national interest.
The announcement came after the cabinet held an emergency meeting on Saturday.
Mr Mikati said he had agreed to remain in his post, adding that Lebanon needed to remain unified, strong and secure.
Officials later said Friday's car bombing had left three people dead - revising the death toll down from eight. More than 80 people were wounded.
The blast occurred in a busy street in Beirut's mainly Christian district of Ashrafiya, creating widespead destruction.
No group has said it carried out the attack. Mr Hassan - described by officials as the main target - had close links with opposition leader Saad Hariri, a leading critic of the government in neighbouring Syria.
Mr Hassan led an investigation that implicated Damascus in the 2005 bombing that killed Mr Hariri's father, former Prime Minister Rafik Hariri.
He also recently organised the arrest of a former minister accused of planning a Syrian-sponsored bombing campaign in Lebanon.
Opposition supporters have set up roadblocks and burnt tyres in Beirut, denouncing Syrian President Bashar al-Assad and his Lebanese allies.
Similar protests are being held in Sidon in the south, Tripoli in the north and in the Bekaa Valley in the east.
Saad Hariri has urged people to turn out in large numbers for Wissam Hassan's funeral in Beirut on Sunday.
'Guarantor of security'
Tension in Lebanon has been rising as a result of the Syrian conflict.
"We accuse Bashar al-Assad of the assassination of Wissam al-Hassan, the guarantor of the security of the Lebanese," Mr Hariri said on Lebanese TV.
Druze leader Walid Jumblatt told satellite channel Al-Arabiya: "[Bashar al-Assad] is telling us that even though he turned Syria into rubble, 'I am ready to kill in any place.'"
Nadim Gemayel, an MP from the right-wing Christian Phalange Party, also pointed to Syria, where the 18-month old uprising against Mr Assad has turned increasingly violent.
"This regime, which is crumbling, is trying to export its conflict to Lebanon," he said.
Mr Hariri's 14 March bloc issued a statement accusing the Beirut government of protecting "criminals" and calling on it to stand down.
Mr Mikati said the government was trying to identify the perpetrators and they would be punished.
Lebanon's Shia militant group Hezbollah - a close ally of the Syrian government - condemned the bombing.
Syrian Information Minister Omran al-Zoubi called it a "cowardly, terrorist act". He said such incidents were "unjustifiable wherever they occur".