The death toll from Sunday's violence climbed to near 50, but it was not known how many civilians have been killed inside the Nahr el-Bared camp on the outskirts of the northern port city of Tripoli, the scene of the heaviest fighting. No new deaths on Monday have been reported.
Lebanese officials said one of the men killed Sunday was a suspect in a failed German train bombing — another indication the camp had become a refuge for Fatah Islam militants planning attacks outside of Lebanon. In the past, others affiliated with the group in the camp have said they were aiming to send trained fighters into Iraq and the group's leader has been linked to al-Qaeda in Iraq.
Hundreds of Lebanese army troops, backed by tanks and armored carriers, surrounded the refugee camp early Monday. M-48 battle tanks unleashed their cannon fire on the camp, sending orange flames followed by white plumes of smoke. The militants fired mortars toward the troops at daybreak.
An army officer at the front line said troops directed concentrated fire at buildings known to house militants in the camp. He said troops also had orders to strike hard at any target that directed fire back at them.
"Everything we know that they were present in has been targeted," he told The Associated Press, speaking on condition of anonymity because he was not authorized to talk to the media.
A spokesman for Fatah Islam, Abu Salim, warned that if the army bombardment did not stop, the militants would step up attacks by rockets and artillery "and would take the battle outside Tripoli."
He did not elaborate on the threat, holding authorities responsible for the consequences.
"It is a life-or-death battle. Their aim is to wipe out Fatah Islam. We will respond and we know how to respond," he told the AP.
Earlier in the day, another refugee camp, Ein el-Hilweh in southern Lebanon, was tense after Lebanese troops surrounded it and armed militants went on alert.
Conflicting reportsAt least 27 soldiers and 20 militants were killed Sunday, Lebanese security officials said. But they did not know how many civilians had been killed in the camp because it is off-limits to their authority.
There were conflicting reports Monday about the arrangement of a truce that medical officials on the camp's edge said would allow the distribution of food and supplies and the evacuation of the wounded. Army officials said there was no cease-fire in place yet, but Hamas' Lebanon representative, Osama Hamdan, said an agreement was reached.
The clashes were triggered when police raided suspected Fatah Islam hideouts in several buildings in Tripoli, searching for men wanted in a recent bank robbery. A gunbattle erupted at one of the buildings between the group's fighters, and troops were called in to help the police.
Militants then burst out of the nearby refugee camp, seizing Lebanese army positions, capturing two armored vehicles and ambushing troops. Lebanese troops later laid siege to the refugee camp where Fatah Islam militants were believed to be hiding, unleashing fire from tanks, artillery and heavy machine guns.
It was unclear whether Lebanese authorities had known El-Hajdib's whereabouts, or the whereabouts of the group's leader, a Palestinian named Shaker al-Absi, before the gunbattle first broke out in Tripoli.
Al-Absi, wanted in three countries, told The New York Times in March that he was trying to spread al-Qaeda's ideology and was training fighters inside the camp for attacks on other countries.
He would not specify which countries but expressed anger toward the United States. And he was sentenced to death earlier in absentia along with Abu Musab al-Zarqawi, the leader of al-Qaeda in Iraq killed last summer by U.S. forces in Iraq, for the 2002 assassination of an American diplomat in Jordan.
Al-Absi had been in custody in Syria until last fall but was released and set up his group in the camp, where he apparently found recruits, Lebanese officials said.
Lebanon's national police commander, Maj. Gen. Ashraf Rifi, said Damascus was using the Fatah Islam group as a covert way to wreak havoc in the country. He denied Fatah Islam's al-Qaeda links, saying it was a Syrian-bred group.
"Perhaps there are some deluded people among them but they are not al-Qaeda. This is imitation al-Qaeda, a 'Made in Syria' one," he told the AP.
Lebanese security officials said Fatah Islam has up to 100 members who come from Arab countries, including Saudi Arabia and Syria, as well as local sympathizers who belong to the conservative Salafi branch of Islam.
The Lebanese Broadcasting Corp. TV station reported the dead militants included men from Bangladesh, Yemen and other Arab countries. Some of those killed were wearing explosive belts, security officials said.
Officials identified the suspect in the failed German train bombing as Saddam El-Hajdib, the fourth-highest ranking official in the Fatah Islam group, an official said Monday. The official spoke on condition of anonymity because he was not authorized to speak to the media. El-Hajdib had been on trial in absentia in Lebanon in connection with the failed German plot.
Mohammed Hanafi, identified by Al-Jazeera as a human rights activist in the camp, said 34 people had been killed inside, including 14 civilians, and 150 wounded. But that could not be independently confirmed and other estimates of civilian deaths were lower.
Ahmed Methqal, a Muslim cleric in the camp, told Al-Jazeera that five civilians had been killed.
"You can say there is a massacre going on in the camp of children and women who have nothing to do with Fatah Islam," he said. "They are targeting buildings, with people in them. What's the guilt of children, women and the elderly?"
He said sniper fire had confined the camp's 30,000 residents to their houses.
Lebanon has struggled to defeat armed groups that control pockets of the country — especially inside the 12 Palestinian refugee camps housing 350,000 people, which Lebanese authorities can't enter.
Some camps have become havens for Islamic militants accused of carrying out attacks in the country and of sending recruits to fight U.S.-led coalition forces in Iraq.
Palestinian officials in the West Bank sought to distance themselves from Fatah Islam and urged Palestinian refugees in the camp to isolate the militant group.
Palestinian officials who met Monday with Lebanese Prime Minister Fuad Saniora said he was focused on saving lives and left it to him to decide whether to send the army into the camp.
"Entering the camp does not mean it will be easy to get rid of this (Fatah Islam) phenomenon," PLO representative Abbas Zaki warned.
Lebanese Sunni political and religious leaders backed the army and the government.
Late Sunday, an explosion across the street from a busy shopping mall in the Christian sector of Beirut killed a 63-year-old woman and injured 12 other people, police said.
Beirut and its suburbs have seen a series of blasts in the last two years, many targeting Christian areas. Authorities blamed Fatah Islam for Feb. 13 bombings of commuter buses that killed three, but the group denied involvement.
Syria has denied involvement in any of the bombings.