BEIRUT, Lebanon — Lebanon’s army appeared Wednesday to be gearing up to launch a major assault on a Palestinian Arab refugee camp where troops have been battling Islamic militants for weeks.

Witnesses said the army was bringing in heavy reinforcements to the Nahr el-Bared camp area near the northern port of Tripoli, suggesting a fresh assault was imminent.

A sniper from inside the camp killed a Lebanese soldier late Tuesday after the Fatah Islam fighters rejected repeated calls to surrender.

Also on Wednesday, three ambulances belonging to the Palestinian Red Crescent society entered the besieged camp to evacuate civilians still trapped inside who wished to leave. The mainstream Palestinian Arab Fatah movement was reported to have called on its guerrillas inside the camp to leave as well.

An International Committee of the Red Cross communications officer, Samar Kadi, said 140 men, women and children, including Fatah members, were evacuated in Red Crescent vehicles. Kadi said the process was still going on.

Fighting between Fatah Islam and the Lebanese army erupted May 20. Lebanon’s defense minister announced June 21 that the Al Qaeda-inspired militants had been defeated and declared major combat over after soldiers seized militant positions on the edges of the camp.

However, Fatah Islam fighters fled deeper into the camp and continue to engage the army in daily firefights. They have repeatedly ignored calls from the army to surrender, and all mediation efforts to end the military standoff have failed.

The battle to drive the Islamic militants out has led to significant damage to parts of the camp, once home to some 30,000 Palestinian Arab refugees. Only a few thousand remain inside, after most residents fled to the nearby Beddawi refugee camp.

A senior military official said the Lebanese soldier was killed late Tuesday near the Nahr el-Bared camp by Fatah Islam snipers inside the settlement.

His death brought to 86 the number of Lebanese soldiers who have been killed since the fighting erupted, said the official, who spoke on condition of anonymity because he was not authorized to give official statements.

Fatah Islam group is believed to be made up of mostly foreign Sunni Muslim fighters, and Lebanon’s Western-backed government has accused the group of trying, with Syria’s backing, to launch a rebellion in the north of the country and destabilize Lebanon. Syria denies the allegations and has described Fatah Islam as a dangerous terrorist organization.

The fighting at the Palestinian Arab refugee camp has become the worst internal violence since Lebanon’s 1975-90 civil war, and is believed to have killed more than 162 people, including 86 soldiers, at least 60 militants and more than 20 civilians.