Renewed gunfire and shelling on Monday forced many terrified residents to flee their homes in the camp, which is home to more than 63,000 people, according to the United Nations Relief and Works Agency for Palestine Refugees in the Near East (UNRWA).

Five members of the Fatah group and one fighter from the Junud al-Sham armed group were among those killed in the clashes, officials said.

Local media reported that more than 40 people, including children, have been wounded in the camp near the southern Lebanese port city of Sidon.

The violence began on Saturday when an unknown gunman tried to kill a member of an armed group named Mahmoud Khalil but instead fatally shot his companion.

In the clashes that followed, Fatah commander Abu Ashraf al-Armouchi and several of his aides were killed. Al-Armouchi was in charge of security inside Ein el-Hilweh.

In a statement carried by the Palestinian news agency WAFA, the Palestinian presidency denounced “the heinous massacre and the terrorist assassination of national security forces who were working hard to maintain the safety and security of the camp and its residents”.

The security of Palestinian camps in Lebanon is a “red line”, it added.

UNRWA said it has suspended services within the camp due to the violence but had opened its schools to families fleeing the fighting. More than 2,000 people fled their homes, it added.

The densely populated camp has been the scene of violent infighting between Palestinian factions over decades.

So what is the history of the camp, why does fighting continue to break out there and what is the significance of the latest confrontations?

What’s the Ein el-Hilweh camp?

Like many other Palestinian refugee camps in Lebanon and neighbouring countries, Ein el-Hilweh was established in the aftermath of the 1948 Nakba, which means “catastrophe”.

The Nakba was the expulsion of at least 750,000 Palestinians from their homes, villages and towns by Zionist militias during the establishment of the Israeli state.

Ein el-Hilweh was originally established by the International Committee of the Red Cross, and most of its early inhabitants had been displaced from northern Palestinian coastal towns.

Now its residents include a large number of Palestinian refugees who were displaced during the Lebanese Civil War and in the aftermath of the Nahr el-Bared conflict in 2007 when fighting broke out between Fatah al-Islam, an armed group, and the Lebanese army.

The refugee population in Ein el-Hilweh continued to grow after 2011 when Syria’s civil war broke out after Bashar al-Assad cracked down on anti-government protests. Millions of people were displaced, including Palestinian refugees who were residing in Syria. Many sought safety in Lebanon and resettled in the camp.

The camp is surrounded by a large wall, and access is limited. Materials used for building and construction are regulated by the Lebanese army, which manages several checkpoints that lead to the camp.

Due to a longstanding agreement, the Lebanese army does not enter the camp, leaving its internal security in the hands of Palestinian factions inside.

An additional 11 official refugee camps are registered under UNRWA across Lebanon. They house almost half a million Palestinians. They live in squalid conditions under a variety of legal restrictions, including on employment.

What’s the history of fighting at Ein el-Hilweh?

Ein el-Hilweh has seen many eruptions of violence over the decades. The camp has seen factional fighting and has been a battlefield between Palestinian factions and Lebanese forces.

In 1974 during the Lebanese Civil War, dozens of Israeli fighter jets bombed and strafed Palestinian refugee camps in Lebanon, predominantly the Ein el-Hilweh camp, in attacks billed as a response to an earlier bombing.

Several people were killed and dozens were wounded in what at the time were believed to be the heaviest air attacks ever carried out in Lebanon.

About 20,000 people are estimated to have lived in the Ein el-Hilweh camp at the time, many of whom saw their closely packed living quarters damaged or destroyed by the Israeli bombs and rockets.

In 1982, during the Israeli invasion of Lebanon, the Israeli army heavily bombed the camp, leaving half-destroyed buildings standing in a sea of rubble.

The fighting that led to the near destruction of the camp, which was home to about 25,000 residents at the time, lasted for several days, and the number of those killed or wounded remains unclear.

Dozens more Israeli air strikes were recorded in the decade that followed, including after Israel’s retreat from Beirut in 1985.

The camp and it surrounding areas also became scenes of battle between Palestinian fighters and the Lebanese army in the early 1990s that left dozens dead amid the instability that followed the end of the long-running Lebanese Civil War.

Since then, factions have fought for dominance within the camp, and have also cracked down on armed groups and fugitives seeking shelter in the camp’s overcrowded neighbourhoods.

In 2017, Palestinian factions engaged in almost a week of fierce clashes with an armed group affiliated with ISIL (ISIS).

What happened in the latest fighting?

Fighters linked to the Fatah faction have increasingly gained prominence in Ein el-Hilweh in recent years.

During fighting between members of Fatah and the Islamist group Junud al-Sham over the weekend, a mortar shell hit a military barracks outside the camp and wounded one soldier, whose condition is stable, the Lebanese army said in a statement.

Factions within the camp used assault rifles and rocket-propelled grenade launchers and lobbed hand grenades in the narrow streets of Ein el-Hilweh.

The violence lasted several hours and prompted some residents in the Sidon neighbourhoods near the camp to flee their homes. Two UNRWA-run schools were damaged.

The fighting drew condemnation from caretaker Prime Minister Najib Mikati, who called on Palestinian leaders to cooperate with the Lebanese army to contain the situation.