SAN'A, Yemen (AP) — Thousands of people have fled a village in southern Yemen where security forces are laying siege to al-Qaida militants, a security official said Monday, signaling an escalation in the government's U.S.-backed campaign to uproot the terror network's local offshoot.

Government forces have moved into the village of Hawta with tanks and armored vehicles and 90 percent of its residents have fled, said Abdullah Baouda, police chief for the surrounding district.

One family fleeing Hawta said forces have shelled the village indiscriminately for the past two days to flush out the militants. Troops also fired on vehicles of residents fleeing the village and another nearby trouble spot, the city of Lawder, killing two civilians and wounding three others, according local government and medical officials.

Hawta is in Yemen's mountainous Shabwa province, one the areas where al-Qaida in the Arabian Peninsula has taken root over the past year and a half beyond the reach of a weak central government that has little control beyond the capital.

The United States is deeply concerned about the threat from Yemen's al-Qaida branch. The group claimed responsibility for the December attempt to blow up a Detroit-bound airliner, linking the plot to Yemen's cooperation with the U.S. military in strikes on al-Qaida targets.

The U.S. has shared intelligence and provided financial aid and training to Yemeni forces, generating backlash among Yemenis who feel their government is too closely allied with America.

Around 120 al-Qaida militants are believed to be taking refuge in Hawta, the police chief said. Three militants were killed and four were wounded in the fighting, said the provincial governor, Ali Hassan al-Ahmadi. One anti-terrorism officer was injured, he said.

"The siege will remain until those elements hand themselves in and we manage to uproot terrorist groups from the region," al-Ahmadi said.

For months, al-Qaida in the Arabian Peninsula has hammered Yemen's security forces in attacks on checkpoints and other security outposts.

The group said in an Internet statement Monday that it abducted a senior security official and demanded the release of two of its imprisoned members within 48 hours. Brig. Ali Hossam disappeared Aug. 26. The group did not say what it would do if its demand was not met.

Yemen's government has had trouble gaining control of areas in the south that are under the control of powerful tribes, some sympathetic to al-Qaida and other Islamic militants roaming the area.

Yemen is the poorest nation in the Arab world and is beset by other major internal security threats — an on-and-off rebellion on the north and a separate secessionist movement in the south.

In the capital, four al-Qaida suspects, including a Yemeni-German teenager, were brought to trial Monday on charges of plotting attacks on tourists, international institutions and security forces.

A court official said the 16-year-old dual national, Rami Hans Harman, denied the charges and told the court that authorities extracted a false confession from him while he was blindfolded.

The four men are also charged with setting up training camps and forming terrorist cells in southern Marib province.

The court official spoke on condition of anonymity because he was not authorized to speak to the press.

The U.S. has pledged $150 million in military assistance to Yemen this year for helicopters, planes and other equipment to battle al-Qaida. Recently, U.S. officials have said they are looking at using armed Predator drones to hunt down and kill al-Qaida leaders operating out of safe havens in Yemen's ungoverned regions, if the country's leaders agree.

President Barack Obama's counterterrorism adviser, John Brennan, visited Yemen Monday for talks with President Ali Abdullah Saleh and other senior officials. He delivered a letter to the president from Obama, the U.S. Embassy said.

In it, Obama assured Saleh the United States was committed to supporting Yemen's people, who he said could do more than just "overcome the threats that they face — they can build a future of greater peace and opportunity for their children."