A plume of smoke rose above the scene in the north of the Afghan capital, which has been hit by a series of recent suicide strikes including on the Supreme Court, the airport and close to the presidential palace.
"Four Nepalese guards, one Afghan guard and two Afghan civilians have been killed," Kabul police chief Mohammad Ayoub Salangi told AFP after the attack at about 4:30 am (midnight GMT).
Up to four other people were wounded. An AFP photographer saw one badly shaken guard being helped from the site with bloody face wounds and a bandage wrapped around his head.
Salangi said that the attack started with a suicide bomb carried in a large truck, then two or three insurgents fought with guards for about 30-40 minutes. All the assailants were killed.
The blast left a large crater in the ground and reduced walls and a guard post to a pile of rubble and twisted steel.
Police said the attack targeted a transport logistics company working with international forces and that some suicide vests were later detonated by security forces.
There was no immediate claim of responsibility, but Taliban insurgents have said they were behind the spate of strikes in Kabul, which come as pressure grows on the Afghan government to seek a peace deal with the rebels.
The US has been pushing for peace talks to start as 100,000 NATO combat troops prepare to withdraw next year and Afghan forces take on the fight against the Islamist extremists.
But a Taliban office in Qatar that opened on June 18 to foster peace talks enraged President Hamid Karzai as it appeared to be an unofficial embassy for a government-in-exile.
He broke off bilateral security talks with the Americans and threatened to boycott any peace process altogether.
The Taliban, who have been fighting a guerrilla war for 12 years, have consistently refused to hold any talks with the Afghan government, with rebel leaders labelling Karzai as a puppet of the United States.
But the Pentagon on Monday expressed optimism over negotiations for a security deal, which would set the size of a "residual" US force to stay in the country and would provide legal immunity for US forces.
NATO commanders, the Afghan government and the Taliban have all vowed to keep fighting at the same time as international efforts are made to secure a ceasefire and revive the peace process.
Only hours after the Qatar office opened, a Taliban rocket attack killed four Americans on the largest military base in Afghanistan. Days later, a suicide squad targeted the presidential palace and a CIA office in the most audacious assault in Kabul in years.
US President Barack Obama recently said he anticipated "a lot of bumps in the road" but that a peace settlement with the Islamist militants was the only way to end violence in Afghanistan.
More than 3,300 coalition personnel have been killed in Afghanistan since 2001, peaking at 711 deaths in 2010, according to the independent icasualties.org website.
Half of the 68,000 US troops in Afghanistan will exit by February, and the newly trained Afghan army and police are increasingly taking the lead across the country in the battle to suppress the Taliban.
The Taliban were deposed in 2001 for sheltering Al-Qaeda leaders behind the 9/11 attacks on New York and Washington.