Gunmen riddled the car of Yemen's information minister with bullets as he left a cabinet meeting in the capital on Tuesday but he escaped the assassination attempt unhurt, an aide said.

In southern Yemen, at least 12 al Qaeda militants, including four local leaders, were killed in a drone strike in south Yemen. It was one of the biggest such strikes believed to have been carried out by the United States in Yemen.

Both incidents highlighted the multiple security problems in Yemen that have alarmed regional power Saudi Arabia and the United States.

In the capital Sanaa, unidentified assailants opened fire on Information Minister Ali al-Amrani's car as he prepared to leave from a cabinet meeting. The minister was not hurt, according to his secretary, Abdel-Basset al-Qaedi.

It was not immediately clear who was behind the attack on Amrani, who quit outgoing President Ali Abdullah Saleh's ruling General Peoples Congress (GPC) party following the outbreak of protests against his long rule and joined his opponents.

He was named information minister in a coalition government between the opposition and the GPC after Saleh signed a deal to transfer power to his deputy, Abd-Rabbu Mansour Hadi, in a move aimed at averting civil war.

Between 12 and 15 people were killed in the drone attack on militants travelling in two vehicles, a tribal leader told Reuters. The dead included at least four leaders of Yemen-based al Qaeda in the Arabian Peninsula (AQAP), he said.

Residents said the drone hit the militants overnight east of Lawdar in Abyan province. No civilians were hurt, they said.

This can be considered as one of the biggest American strikes because it targeted a large number of al Qaeda leaders at the same time, the tribal leader, who declined to be identified, told Reuters by telephone.

Unlike in previous attacks, this one seems to have achieved its goals and, unlike previous attacks, it did not result in civilian casualties.

In one of the deadliest strikes in late 2009, more than 40 civilians, including women and children, died in an air strike that Washington said targeted al Qaeda.

Al Qaeda militants have regrouped in the mountains of Yemen after suffering blows in Saudi Arabia and Iraq over the past few years. They exploited months of protests against Saleh last year to broaden their hold on swathes of territory in Yemen's south.

Tribal leaders said one of those killed was Abdel-Munem al-Fatahani, who was wanted over attacks on the U.S. destroyer Cole in 2000 and a French oil tanker in 2002.

Militants denied that Fatahani or any local al Qaeda leader was killed and said only foot soldiers died. But a tribal chief and witnesses insisted Fatahani was among the dead, saying the militants had closed off the areas and quickly buried the dead.

Separately, tribesmen kidnapped six foreign aid workers from a tourist area west of Sanaa on Tuesday. State news agency Saba said the abductees were a German, a Colombian, an Iraqi, a Palestinian and two Yemenis.

A U.N. source said the six worked for the world body's Office for the Coordination of Humanitarian Affairs (OCHA).

OCHA spokeswoman Elisabeth Brys told Reuters in Geneva: The only information we have for now is that there has been an incident. We are looking into it.

In a sign of increased security problems, gunmen held up a Saudi diplomat as he drove through the southern city of Aden, a security official said. The diplomat was not hurt.

U.S., SAUDI ARABIA WORRIED

The United States has repeatedly used drones in Yemen to attack militants from AQAP, described by CIA Director David Petraeus recently as the most dangerous regional node in the global jihad.

In testimony to the U.S. Congress in September, Petraeus said that AQAP was behind the December 2009 plot to blow up a U.S. airliner as it approached Detroit and a 2010 effort to send bombs hidden in computer printers on two cargo aircraft.

Al Qaeda militants already dominate considerable territory in southern Abyan province and the their brief capture of the town of Radda underscored concerns that protracted political upheaval in Yemen over the fate of Saleh could give al Qaeda's regional wing a foothold near Red Sea oil shipping routes.

Protests have continued since Saleh transferred his powers and activists are pressing demands that Saleh, who is in the United States for medical care, be tried for alleged killings of protesters and the government be purged of his relatives.

In a separate incident on Tuesday, Yemeni security sources said that at least three al Qaeda militants were killed in a clash with government soldiers outside Radda, about 170 km (105 miles) southeast of Sanaa.

The sources said five Yemeni soldiers were wounded in the clash, which targeted Tareq al-Dahab, a relative of assassinated U.S. citizen and al Qaeda cleric Anwar al-Awlaki. Dahab, who led the assault on Radda in early January, was not hurt in the clash, but tribal sources said five Yemeni soldiers also died.

(Additional reporting by Stephanie Nebehay in Geneva; Writing by Sami Aboudi and Firouz Sedarat; Editing by Mark Heinrich)