Afghan troops arrive at Kabul's main military hospital on Saturday after a fatal explosion. (Mustafa Quraishi/AP)

In the latest sign of rising violence in Afghanistan, a suicide bomber blew himself up inside the compound of the main military hospital in the capital Saturday, killing six people. And on Sunday, gunmen wearing suicide vests stormed a government building in the eastern part of the country in the early morning and began a shootout with Afghan security forces who surrounded the compound, officials said.

The Saturday attack, in which 23 people were wounded, targeted a tent where medical students were having lunch on the grounds of the Mohammad Daud Khan hospital, which lies in a mostly secure part of Kabul near the U.S. Embassy and other diplomatic missions.

Gen. Mohammad Zaher Azimi, a Defense Ministry spokesman, said the dead and wounded were civilians training to become military doctors and that officials are investigating how the bomber made his way through the secured complex.

In Sunday’s attack, the Associated Press reported, one guard was killed as three or four gunmen wearing explosives strapped to their bodies shot 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.

He said the gun battle 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, the wire service reported.

Afghan security forces had the compound surrounded, provincial Police Chief Gen. Abdul Hakim Ishaqzai said. No one immediately claimed responsibility for the Sunday attack, but it matched the pattern of Taliban assaults on government installations, AP said.

The Taliban, which has spearheaded the insurgency against the Afghan government and foreign troops, asserted responsibility for the hospital bombing. Zabihullah Mujahid, a spokesman for the group, did not say whether the bomber had made his own way through the facility or had done so after infiltrating Afghan forces.

Rogue Afghan forces and Taliban infiltrators have carried out a string of attacks on joint Afghan and foreign bases across the country in recent weeks, killing both Afghan and foreign troops.

The deadliest attack came late last month when a veteran Afghan pilot killed nine American mentors, one of them a contractor, at Kabul’s airport. Earlier in April, a gun battle erupted inside the Defense Ministry when a suicide bomber tried to kill top ministry officials. The attacks have raised questions about the ability of Afghan forces to gradually take over from the NATO-led troops as the United States plans to reduce its military presence from July onward.

Overthrown in a U.S.-led invasion backed by Afghan forces, the Taliban has made a comeback in recent years and this month vowed to launch a massive spring offensive against Afghan and foreign troops.

Salahuddin and Hamdard are special correspondents. Correspondent Joshua Partlow in Khost, Afghanistan, contributed to this report.