An unidentified warplane attacked the presidential palace in Aden on Thursday after rival forces fought the worst clashes in years in Yemen's second city, an official and residents said, in a sharp escalation of the country's months-long armed turmoil.

Thirteen people were killed when forces loyal to President Abd-Rabbu Mansour Hadi fought their way into Aden's international airport and wrested an adjacent military base from a renegade officer, Aden governor Abdulaziz bin Habtoor said in a televised speech.

Both the fighting on the ground and subsequent air attack on Hadi's compound appeared to be part of a deepening power struggle between Hadi and the Shi'ite Muslim Houthi group, which controls the capital Sanaa and is allied with former president Ali Abdullah Saleh.

The aircraft dropped a bomb or fired a missile at the compound in al-Maasheeq district of the southern port city, where Hadi is based, the Yemeni official said,

Residents said anti-aircraft guns opened fire at the plane, and smoke was seen rising from the area, but it was not immediately clear if Hadi was in the compound. A second approach by a warplane was repelled by anti-aircraft fire, they said.

An aide to Hadi said the president was "safe at a secure location ... There was a raid, but there were no casualties."

BUSY FLIGHTS OVER SANAA

A Yemeni security source said the situation at the palace "was under control and there was nothing to be worried about".

The identity of the aircraft was not immediately known, but residents in Sanaa, which is under control of the Houthi group said they saw an unusually busy level of flights by military aircraft in the skies of the capital.

Earlier in the day, soldiers and militiamen loyal to Hadi using tanks and armoured vehicles fought their way into Aden's airport and stormed the nearby military base, residents said.

General Abdel-Hafez al-Saqqaf had been holed up for days in the base after he refused an order by Hadi to hand over control of the Special Forces in the city to another commander, a senior security source said.

The fighting brought traffic at the airport to a halt.

Witnesses said many Special Forces soldiers had been taken prisoner at the al-Sawlaban base in the Khor Maksar district.

RENEGADE CAMP

"Saqqaf's mutiny is over," a senior officer said.

Saqqaf later turned himself in to the governor of the adjacent Lahj province, the Aden al-Ghad newspaper reported.

In a statement, the Houthi-led Supreme Security Committee urged an end to the Aden fighting, saying both sides "are obliged to keep the peace and return to the negotiating table".

The growing instability in Aden has overshadowed a vigorous campaign of attacks by al Qaeda, long seen by Washington as the main threat to the country, which shares a long border with the world's top oil exporter, Saudi Arabia.

Tensions have been heightened in Aden since Hadi fled there in February after escaping a month of house arrest in Sanaa by Houthi forces who seized Sanaa last September. Hadi has been trying to consolidate his control over Aden, the better to mount a challenge to Houthi ambitions to control the country.

Reuters