There have been renewed heavy exchanges of gunfire at a Palestinian refugee camp in northern Lebanon where Islamist militants are defying Lebanese troops.
Thousands of Palestinian refugees are still trapped inside the camp
The barrage of machine-gun fire and shells at the Nahr al-Bared camp lasted for some 20 minutes before dying down.
Thousands of people have fled the camp as aid workers struggle to deliver food and medicine to thousands still inside.
Earlier, Lebanese Prime Minister Fouad Siniora vowed his government would not "surrender to terrorism".
Mr Siniora said he would end the conflict "without hesitation" and described the militants from the Fatah al-Islam group in the camp as a criminal gang hiding behind Islam and the Palestinian cause.
The fighting erupted at about 2030 local time (1730 GMT), a Lebanese army spokesman was quoted by the AFP news agency.
Lebanese army officials said the shooting began from inside the camp and that the troops returned fire.
But Fatah al-Islam spokesman Abu Salim Taha told the al-Jazeera Arabic television from inside the camp that the army had opened fire.
The fighting came on the fifth day of the stand-off between the Lebanese army and the Fatah al-Islam, ending a two-day period of relative calm.
The BBC's Jon Leyne close to Nahr al-Bared says the Lebanese army is in position in force outside the camp; inside, the militants are determined not to surrender.
At least 50 soldiers and militants have been killed in the fighting at the camp so far. The civilian death toll is not known.
The fighting at the camp is the bloodiest internal conflict in Lebanon since the civil war ended 17 years ago.
It began after security forces raided a building in Tripoli to arrest suspects in a bank robbery. Fatah al-Islam militants then attacked army posts at the entrances to the camp.
A large force of Lebanese troops hit back, bombarding the camp and storming a building on the outskirts of Tripoli.
Fatah al-Islam is a radical Palestinian splinter group alleged to have links with al-Qaeda. Lebanese officials also believe it is backed by Syria.
Other Palestinian factions have distanced themselves from the group, which emerged last year.