A team of suicide attackers armed with rifles and disguised in police uniforms stormed a traffic police headquarters in east Afghanistan on Sunday, killing five members of the security forces.
The attack in the restive Khost province, which borders Pakistan, came the day after six medical students were killed and 23 wounded when a suicide bomber struck at Kabul's heavily-guarded main military hospital.
Sunday's attack started around 4:30 am (0000 GMT) and initially left three police dead, although sporadic gunfire continued for hours afterwards.
Around nine hours later, Afghan and foreign forces stormed the building where four suicide attackers were holding out.
The resulting fighting killed another policeman and an Afghan soldier as three of the bombers detonated their explosives in the basement of the building, said provincial police chief Abdul Hakim Ishaqzai.
"The joint forces are still trying to kill or capture the fourth suicide attacker. The operation is still ongoing," he added.
A total of seven people have also been wounded in the attack, according to officials.
This includes five police, one Afghan soldier and one civilian.
Deputy provincial police chief Mohammad Yaqub said four attackers forced their way into the building in the early hours while it was vacant except for the police guards and officers on duty.
Yaqub said the attackers were dressed in border police uniform and were armed with vests and AK-47 rifles.
Although there was no immediate claim of responsibility for the latest incident, there has been a string of recent targeted, high-profile attacks in Afghanistan by Taliban who have managed to penetrate supposedly secure official premises.
Last month, three people died when an attacker got inside the defence ministry in Kabul and the police chief of Kandahar province was killed by his bodyguard.
Afghanistan's security forces are frequently targeted by the Taliban and other militants.
The Afghan police and army are to take on more responsibility for security as foreign combat troops withdraw in a process starting from July but not due to be completed until 2014.
There are currently around 130,000 international troops in Afghanistan, the bulk of them from the United States.
The war started following a US-led invasion which ousted the Taliban from power in the wake of the September 11, 2001 attacks in the United States.
At least six people including two women have been killed in other incidents across Afghanistan over the weekend.
Three Afghan policemen were killed and three were wounded late on Saturday when their vehicle was struck by a roadside bomb in the western province of Herat, provincial police spokesman Noor Khan Nikzad told AFP.
They had been on their way to provide back up and support to a police outpost that came under attack in the same area, he added.
In another incident, a border police officer was killed late Saturday when his vehicle was struck by a roadside bomb in the Spin Boldak district of Kandahar, one of the main battlegrounds in the south, the province's police chief Shair Shah Yousufzai told AFP.
Two female civilians died and five others including four women were wounded in the southern province of Zabul on Sunday when the tractor they were travelling hit a roadside mine, the interior ministry in Kabul said.