By Mohammed Ghobari and Mohammed Mukhashaf
SANAA/ADEN, March 10 (Reuters) - U.S. drone attacks killed at least 25 al Qaeda-linked fighters including one of their leaders while a Yemeni air force raid killed 20 more in the south, sources said on Saturday, in the biggest airstrikes since Yemen's new president took office.
Militants have expanded their operations in southern Yemen during months of turmoil which paralysed the country and eventually unseated former President Ali Abdullah Saleh, who was replaced in a February vote by Abd-Rabbu Mansour Hadi.
Local residents in Jaar, a southern town seized by militants in March last year, said Yemen's air force had killed 20 al Qaeda-linked fighters at a military base, also destroying weapons and military equipment.
Last week, the fighters had seized the base from the government and confiscated weaponry and military equipment.
However, a spokesman for Ansar al-Sharia (Partisans of Islamic Law) denied its fighters were killed in the raid.
"There was nobody killed in the air strike," he told Reuters by phone.
In a separate incident, a government source said the number of militants killed in an air strike launched late on Friday in Bayda, about 267 km (166 miles) southeast of the capital Sanaa, had risen to 25. He said Hadaar al-Homaiqani, a local al Qaeda leader, was among the Islamist fighters killed.
Tribal sources said the Bayda attacks were carried out by U.S. drone airplanes, but this was not possible to independently confirm. The United States, working with the Yemeni authorities, has repeatedly used drones to attack militants.
"The bodies were recovered on Saturday morning after the cessation of the attacks carried out by U.S. drone airplanes, and the search for the remaining victims is still under way," one of the sources told Reuters on Saturday morning.
Residents earlier said fighter planes had raided the western outskirts of Bayda town where the Ansar al-Sharia militants, who have been fighting Yemen's security forces since mid-2011, had been based.
"Flames and smoke could be seen rising from the area," one resident told Reuters by telephone.
Ansar al-Sharia is inspired by al Qaeda but the precise nature of its ties to the global network are unclear, although the Yemeni government says they are one and the same.
The United States has used its drones repeatedly to attack militants from al Qaeda in the Arabian Peninsula, described by CIA Director David Petraeus last year as "the most dangerous regional node in the global jihad".
In late January, at least 12 al Qaeda militants, including four local leaders, were killed in a drone strike in southern Yemen, which a tribal chief said was a U.S. attack.
The United States and Saudi Arabia, Yemen's neighbour and the world's No. 1 oil exporter, have been deeply worried about the expansion of al Qaeda in Yemen, where the group controls swathes of land near oil shipping routes through the Red Sea.
TWO KILLED IN SOUTH
In another incident, a local security official said two al Qaeda militants were killed late on Friday as they tried to set off a bomb at a security checkpoint at an entry point to the town of Mudiyah in the southern province of Abyan.
The violence in the south highlights one of the many challenges Hadi faces as he tries to stabilise Yemen after a year of political upheaval that ousted Saleh after three decades in power. On Monday, he vowed to pursue militants linked to al-Qaeda to their last hiding place.
The United Nations refugee agency UNHCR warned on Friday Yemen is facing a new wave of internal displacement as tens of thousands of civilians flee tribal clashes in the north and fighting between the government and militants in the south.
It said in the past two weeks alone, 1,800 people have been displaced by the latest escalation in fighting between government troops and militants in the Abyan governorate.
UNHCR said it wants $60 million in 2012 for some 216,000 refugees and almost half a million displaced people in Yemen. (Writing by Martina Fuchs; Editing by Sophie Hares)