The militants, armed with automatic weapons, battled security forces until six blew themselves up and one was shot dead, according to defence officials.
 

They say 14 civilians and three police officers were wounded.

The violence comes amid a rise in attacks ahead of Afghanistan's presidential election due on 20 August.
 

Officials say militants wearing suicide belts and armed with machine guns and rocket-propelled grenades attacked Khost's main police station and nearby buildings on Saturday.
 

Critically wounded

It was unclear how many attackers were involved. Zabihullah Mujahid who claims to be a Taliban spokesman told the BBC from unknown location: "Four of our attackers had entered the city this afternoon."
 

But government officials told the BBC eight militants had attacked various sites, and only one of them managed to get away.
 

One of the 14 civilans wounded in the fighting is in a critical condition, a defence ministry spokesman told the BBC.
 

Khost resident Mohammad Goal Jan described the confusion during the fighting.
 

"I can hear a lot of gunshots and loud explosions from the police chief's office.
 

"Police and army have blocked the main roads. Khost city is empty. There is a lot of confusion at the moment.''
 

One of the presidential candidates, Ramazan Bashardost, was in Khost but was not affected.
 

Previous attacks

The attack is a big blow to the authorities who have promised better security for the elections next month, says the BBC's Bilal Sarwary in Kabul.
 

Such attacks will only add to the worries of local Afghans in the country's restive south-eastern provinces.

Most of them live in a climate of fear. After attacks in Khost, Paktia and Ningarhar provinces recently, security was beefed up specifically on the outskirts of the city which borders Pakistan.
 

According to local residents, all vehicles coming in and out of Khost were checked on regular basis.
 

In May, six people were killed when militants launched simultaneous assaults on government buildings in Khost.
 

Last week at least four security personnel were killed in attacks on Gardez, about 50 miles (80km) northwest of Khost, when militants attacked the police chief's office, a police station and the intelligence directorate, as well as the governor's compound.

Another security personnel died in an attack in eastern city of Jalalabad.