Gunmen wearing suicide vests stormed a government building in eastern Afghanistan early Sunday and engaged in a shootout with Afghan security forces who surrounded the compound, officials said.

The attack came a day after a Taliban suicide bomber infiltrated the capital's main military hospital and killed at least six Afghan medical students.

In Sunday's incident, one guard was killed as the attackers -- three or four men armed with guns and wearing explosives strapped to their bodies -- shot their was into the traffic department compound on the edge of Khost city at about 5 a.m., said Gen. Raz Mohammad Oryakhail, the army commander for Khost province.

The gunbattle was still going on more than two hours later, with the assailants inside the second floor of the building and shooting down at police and soldiers outside, he said.

Police and soldiers were trying to avoid launching a full assault because they didn't want the gunmen to detonate their suicide vests, said provincial Police Chief Gen. Abdul Hakim Ishaqzai. Afghan security forces had the compound surrounded, he said.

No one immediately claimed responsibility for the attack, but it matched the pattern of Taliban assaults on government installations.

On Saturday, a Taliban suicide bomber on a mission to target foreign-run medical teams killed at least six Afghan medical students and wounded 23 others after infiltrating Kabul's main military hospital, officials said.

The bombing was a blow to Afghan and NATO forces who have sharply expanded checkpoints and security cordons in the capital as the Taliban intensifies their attacks ahead of a planned U.S. drawdown in July.

No foreign medical doctors or nurses were among the dead or wounded, Afghan and NATO officials said. There are a number of military doctors and nurses from various NATO countries at the hospital as part of the alliance's mission to train Afghan forces.

All those killed were eating lunch inside a tent used by medical students for meals, Defense Ministry spokesman Gen. Mohammed Zaher said.

The bombing was condemned by Afghan President Hamid Karzai and NATO. The United Nations called it a violation of "international humanitarian law."

The Taliban have stepped up attacks as part of their spring offensive against NATO, Afghan government installations and officials. Insurgents also have promised revenge attacks after the killing of al-Qaida leader Osama bin Laden by U.S. forces in Pakistan earlier this month.

The effectiveness of the Taliban's campaign will in part determine the size of President Barack Obama's planned drawdown of American troops. He has said its size will depend on conditions on the ground.

NATO has committed itself to handing over control of security to Afghans by 2014.

Taliban spokesman Zabiullah Mujahid said Saturday's attack targeted foreign trainers and Afghan doctors who work with them. He claimed two bombers took part, but Defense Ministry spokesman Gen. Mohammed Zaher Azimi said only one was involved in the attack at the Mohammad Daud Khan military hospital.

The Taliban have promised to carry out attacks in major population centers, and earlier this month tried to take over key government installations in the southern city of Kandahar -- which was once their capital and stronghold. But that attack failed and more than two dozen militants were killed.

U.S. and NATO military officials, however, have questioned the Taliban's ability to mount large operations. Thousands of insurgents, including midlevel commanders, have been killed or captured and hundreds of weapons caches seized during battles over the winter.

Lt. Gen. David Rodriguez, the second-ranking U.S. general in Afghanistan, predicted recently that the Taliban -- having lost ground during the fall and winter -- will employ more indirect tactics such as suicide attacks and assassinations.
Mujahid said that was part of the Taliban's strategy against the government. "The mujahedeen are able to infiltrate into the ranks of the enemy and using opportunities are able to attack," he said.

It was unclear whether the bomber was a member of the hospital staff, but the ability of the attacker to get inside the heavily guarded hospital raised fresh concerns about possible infiltration of Afghan security forces. The facility is in one of Kabul's most heavily protected neighborhoods and close to NATO headquarters, the U.S. Embassy and other diplomatic facilities. Security checks are stringent and all visitors are searched.

In the most embarrassing breach of a government facility, a Taliban militant opened fire inside the Afghan Defense Ministry on April 18, killing two Afghan soldiers. At the time, the Taliban said one of their agents who was also an army officer planned the attack to coincide with a visit of the French defense minister, who was not in the ministry at the time.