Two people were killed Saturday in clashes that erupted again after a relatively calm night at Ain al-Helweh, a restive Palestinian refugee camp in Lebanon's south, official media reported.

Fresh violence broke out late Thursday in Ain al-Helweh, on the outskirts of the coastal city of Sidon, just weeks after deadly clashes pitted members of Palestinian president Mahmud Abbas's Fatah movement against Islamist militants.

Ongoing fighting inside the camp on Saturday killed one person and wounded seven others, Lebanon's official National News Agency (NNA) said.

A source in the camp's Palestinian leadership told AFP on condition of anonymity that the man killed was an Islamist militant.

The NNA said a second person was killed and several others wounded outside Ain al-Helweh by stray bullets.

While calm had largely prevailed overnight, heavy clashes broke out on Saturday morning, an AFP correspondent in Sidon said, reporting the sound of automatic weapons and rocket propelled grenades.

A public hospital directly adjacent to the camp transferred all its patients to other facilities due to the danger, its director Ahmad al-Samadi told AFP.

Ain al-Helweh is home to more than 54,000 registered refugees and thousands of Palestinians who joined them in recent years from Syria, fleeing war in the neighbouring country.

The camp, Lebanon's largest, was created for Palestinians who were driven out or fled during the 1948 war that coincided with Israel's creation.

In the worst outbreak of violence in the camp in years, five days of clashes that began in late July left 13 people dead and dozens wounded.

Those clashes erupted after the death of an Islamist militant, followed by an ambush that killed five Fatah members including a military leader.

The United Nations' resident coordinator in Lebanon, Imran Riza, on Friday urged "armed groups to stop the fighting in the camp" and to "immediately" vacate schools belonging to the UN agency for Palestinian refugees, UNRWA.

"The use of armed groups of schools amounts to gross violations" of international law, Riza said in a statement.

Lebanon hosts an estimated 250,000 Palestinian refugees, according to UNRWA.

Most live in one of Lebanon's 12 official camps, and face a variety of legal restrictions including on employment.

By long-standing convention, the army does not enter Palestinian camps -- now bustling but impoverished urban districts -- leaving the factions themselves to handle security.