KABUL, Afghanistan (AP) — Taliban suicide attackers stormed a four-story house used by an American aid organization in north Afghanistan on Friday, killing four people before dying in a fierce, five-hour gunbattle with Afghan security forces.

The pre-dawn attack appeared part of a militant campaign against international development organizations at a time when the U.S. and its allies are trying to accelerate civilian aid efforts to turn back the Taliban.

It came on the same day that Gen. David Petraeus landed in the Afghan capital to take command of U.S. and international forces fighting the nearly 9-year-old war. Petraeus arrived from Brussels where he sought to reassure allies that the war against the Taliban was on track despite rising casualties and problems regaining control over key parts of the country.

Insurgents began their brazen attack in Kunduz at about 3:30 a.m. A suicide car bomber blew a hole in the wall around a building used by Development Alternatives Inc., a global consulting company based in the Washington, D.C., area on contract with the U.S. Agency for International Development, or USAID. The company is working on governance and community development issues in the area.

At least five other attackers, all wearing explosive vests, then ran inside the building, according to Afghan police and army officials. The insurgents killed or wounded security guards and others before dying themselves in a gunbattle with Afghan security forces who raced to the scene.

"It was 3 o'clock in the morning, close to the morning prayer time, when a suicide bomber in a 4x4 vehicle exploded his vehicle," Gen. Abdul Razaq Yaqoubi, police chief in Kunduz province, said as Afghan national security forces were still battling to kill the last surviving attacker. "There is no way for him to escape."

Black smoke billowed from the windows of the house. The bodies of the victims were found laying amid broken glass, rubble and pools of blood. Stunned aid workers were led from the scene as NATO troops carried bodies wrapped in black plastic out on stretchers.

One British, one German and two Afghan nationals were killed, according to a statement issued by DAI in Bethesda, Md. They all worked for DAI's security subcontractor, Edinburgh International, DAI said. Several other people, including two members of the DAI staff, were among those injured.

Steven O'Connor, communications director for DAI, said three DAI employees — two Americans and one Serb — were inside the building at the time of the attack. It was unclear if they were among the wounded.

"The actions taken by the Edinburgh International security staff in defense of the compound and project staff were nothing short of heroic," said DAI President James Boomgard. "We are deeply grateful for their bravery, and for the work they do day in, day out, to make our development mission possible. Our hearts go out to the families of the deceased at this terrible hour."

He said the firm would be working with USAID, Edinburgh International and others to assess the security situation in Kunduz, a focal point of the insurgency in the north.

Taliban spokesman Zabiullah Mujahid told The Associated Press in Kabul that six suicide bombers attacked a "training center" for Afghan security forces in Kunduz and killed 55 foreigners. The Taliban often exaggerate their claims.

Insurgents have been carrying out attacks in recent months against organizations and individuals seen as cooperating with the Afghan government and donor nations just as the international community is trying to help the government of Afghan President Hamid Karzai extend its reach deeper into the provinces.

"They don't want the people of Afghanistan to have a prosperous life," Karzai said in a statement condemning the attack.

The U.S. called it a cowardly attack on civilians working to improve conditions in the nation.

"This is another tragic reminder of the life-threatening circumstances that our Afghan and international partners face every day as they work side by side with the Afghan government and its people to improve conditions in the country for a better future," according to the joint statement issued by USAID and the U.S. Embassy in Afghanistan.

Attacks on U.S. contractors, construction companies and aid organizations have been rising just as the United States pushes faster development of one of the world's poorest countries — a priority in its strategy to counter the insurgency. Many of the recent attacks have occurred in Kandahar province in the south where Afghan and NATO forces are ramping up security to wrest control of the area from insurgents and criminals.

In April in Kandahar, a suicide bombing on a fortified guesthouse shared by Western contracting companies killed four Afghans and injured several Americans; a gunman killed an 18-year-old woman working for DAI as she left her job; and the vice mayor of the city was shot and killed as he prayed at a mosque.

Also in April, five Afghan workers for the U.N. Office of Project Services were taken hostage in Baghlan province, west of Kabul, but were later freed unharmed.

Earlier this week, the Afghan driver of a U.N. vehicle was shot and killed in midday traffic in central Kabul, and militants rocketed a base for South Korean construction workers in Parwan province, north of the capital, but caused no casualties.