ADEN - Yemeni militiamen clashed with soldiers guarding the presidential palace in the southern Yemeni city of Aden on Sunday, a local official and residents said, in a rare confrontation between the previously allied forces.

The embattled Yemen government is based in Aden and has struggled to build up a national military and pay its bills, including to fighters who have fought on its behalf, as Al Qaeda and Islamic State militants have taken advantage of 10 months of civil war to expand their presence in the city.

A local official said the attackers, affiliated with a local militia called the Popular Southern Resistance, sought an audience with top officials inside the palace over unpaid medical bills for guards wounded in an attack there last month.

Six guards were killed and several were wounded in the attack on Jan. 28 at the Maashiq palace in the crater district, for which Yemen’s branch of Islamic State claimed responsibility. “They wanted to discuss compensation for those killed and paying the medical bills for the wounded ... When the guards blocked them, a gun battle erupted involving light and medium weapons,” the official said. Residents in the area reported several casualties in the fighting but could not give precise figures.

A series of attacks by militants have for months rocked the city, where the Saudi-backed President Abd-Rabbu Mansour Hadi and his government are trying to oversee a campaign to dislodge Iran-allied Houthis from the northern half of the country they seized in 2014.

Meanwhile, gunmen killed a pro-government Salafist cleric on Sunday in Yemen's main southern city of Aden, home to a growing militant presence, a security official said.

Sheikh Abdulrahman al-Adani was shot dead as he was heading to a mosque near his home, the official said.

Adani headed a Salafist religious school which attracts both local and foreign students.

He was known for his stance against the Shiite Huthi rebels as well as against the Islamic State group and Al-Qaeda which are becoming increasingly active in Aden, sources there said.

According to Zaid al-Sallami, an Aden-based expert on Islamist groups, Adani was known for "rejecting violence and terrorism".