KABUL: A suicide bomber on a motorcycle killed five foreign security guards and wounded six, the latest blast to rock the Afghan capital during an impasse over presidential election results.

The attacker struck at the gates of the compound, which houses foreign advisers to the Afghan government as well as the office of the deputy minister for counter-narcotics in the heart of the country’s capital, said Deputy Interior Minister Gen. Mohammad Ayoub Salangi.

The nationality of the killed guards was not immediately disclosed.

“The US Embassy strongly condemns the terrorist attack on Camp Gibson in Kabul this morning which killed five foreign national security guards,” a US statement said.

“We offer our condolences to the families of the victims, and hope for the speedy recovery of the Afghans and foreign nationals injured in the attack.”

Taleban spokesman Zabihullah Mujahid claimed responsibility for the attack in a statement sent to media.

A police spokesman, Sayed Mahdi Kazimi, said the attacker managed to reach the entrance gate of the compound and detonated his motorbike packed with explosives in the morning hours.

The Taleban frequently use roadside bombs and suicide attacks against Afghan and NATO forces and government offices in the country.

Half an hour after the motorcycle bombing, another explosion wounded an Afghan civilian, said Hashmat Stanikzai, a spokesman for the Kabul police chief.

The attacks and the violence are shaping up as a major test of the Afghan government’s ability to maintain security in volatile areas after foreign combat troops leave by the end of 2014.

Taleban insurgents oppose the election process, which is currently undergoing an audit of all eight million votes due to a dispute between the two contenders over fraud allegations. It gave no further details on Camp Gibson, but Kabul police said it was a joint compound used by the Interior Ministry’s counter-narcotics department and foreign forces.

“Our initial reports show the explosion took place inside the foreigners’ compound,” Kabul police chief Zahir Zahir told AFP. “The foreigners were exercising inside at the time.”

“Our teams are on the ground investigating how an attacker on a motorcycle entered the compound.”

The nationalities of the victims was not known, and there was no immediate comment from NATO’s International Security Assistance Force (ISAF), which is winding down its mission after a 13-year war against the Taleban.

One government official told AFP that the victims worked for a private contractor. The Taleban used a recognized Twitter account to claim responsibility for the attack, saying 15 “agents” had been killed inside a foreign intelligence base. The insurgents often exaggerate death tolls after attacks.

Afghanistan is on edge as the election dispute between poll rivals Ashraf Ghani and Abdullah Abdullah threatens to trigger instability and revive ethnic tensions that ravaged the country during the 1992-1996 civil war.

NATO combat troops will withdraw from Afghanistan by December, and reports suggest unrest is already worsening nationwide.

Civilian casualties soared by 24 percent in the first half of 2014, according to recent UN figures, while the International Crisis Group has said the “overall trend is one of escalating violence and insurgent attacks.”

The vote audit was part of a deal brokered by US Secretary of State John Kerry to tackle the political crisis as Ghani and Abdullah both claimed victory.

Some 23,000 ballot boxes are being transported by the Afghan army and NATO forces to the capital, where they will be examined at 100 verification stations.

Abdullah led Ghani after the first round of voting but preliminary results of the run-off, announced on July 7, showed Ghani ahead by over one million votes.

Abdullah rejected the result, saying that most of his opponent’s ballots were fraudulent.

Abdullah draws his support from Tajiks and other northern Afghan groups, while Ghani is backed by Pashtun tribes of the south and east.

The recount has already sparked fresh arguments and fallen behind schedule.

The inauguration of President Hamid Karzai’s successor was due on Aug. 2, but has now been delayed.