KABUL (AFP) - Militants launched a gun and suicide attack on an Afghan election commission office in Kabul on Tuesday, police said, less than two weeks before the presidential poll.

The Taleban have vowed a campaign of violence to disrupt the ballot on April 5, urging their fighters to attack polling staff, voters and security forces in the runup to election day.

Blasts were heard at an Independent Election Commission (IEC) office in the western Darulaman area of the Afghan capital, close to the home of Ashraf Ghani, who is seen as a frontrunner in the race to succeed President Hamid Karzai.

"At around 11:35 am (3 pm Singapore time) a suicide bomber blew himself up at the gate of an IEC regional office in Darulaman, and then several other attackers entered the building," Kabul police spokesman Hashmat Estanakzai said.

Interior Ministry spokesman Sediq Sediqqi said on Twitter that two civilians wounded in the attack had been taken to hospital.

Witness Ahmad Sharif, a government employee, said he heard two loud explosions followed by gunfire, and an AFP photographer said firing, at times heavy, was still going on more than an hour after the attack began.

A member of Ghani's campaign team said the former World Bank economist was out of Kabul at the time, campaigning in the eastern province of Paktia.

IEC spokesman Noor Mohammad Noor said security forces had told them their office may be the target of the attack.

"We have spoken to our staff in that office, they are all fine and are in their bunkers," Mr Noor said.

There was no immediate claim of responsibility but suicide bombings have been a key weapon for Taleban militants in their fight against Karzai's government and its foreign backers since 2001.

On Thursday four gunmen stormed Kabul's Serena hotel and shot dead nine civilians including an Agence France-Presse journalist, an attack claimed by the Taleban.

The Serena attack came on the same day that seven Taleban suicide attackers invaded a police station in the eastern city of Jalalabad, killing 10 policemen.

And last Tuesday, a suicide bomber killed 16 people at a crowded market in the northern province of Faryab. There was no claim of responsibility for that attack.

Previous Afghan elections have been badly marred by violence as the Islamist militants displayed their opposition to the US-backed polls.