At least one person was killed and 13 others wounded in an attack Sunday targeting the Kabul office of the running mate of Afghan President Ashraf Ghani, officials said.
The violence came the same day as Afghanistan marked the official start of campaign season for the upcoming presidential elections, serving as a grim reminder of the sort of mayhem and bloodshed that have marred previous polls.
Interior ministry spokesman Nasrat Rahimi said the attack began with a blast in north Kabul near the office for Green Trend, a youth- and reform-focused civil society organisation that Amrullah Saleh heads.
"At around 4:40 pm (1210 GMT), first a blast occurred near Green Trend office... then a number of attackers entered that office," Rahimi said.
Two hours later, the attack was still ongoing.
"The security forces have cordoned off the area. The security forces are trying to kill the attackers as soon as possible," he continued.
No group immediately claimed responsibility for the attack.
Rahimi said Saleh, who has previously served as the head of the country's intelligence agency, was not wounded.
Ejaz Malikzada, a witness, told AFP he had heard three explosions.
"It is a direct attack on the office of the Green Trend," he said. "I have heard three explosions so far, and gunfire is also continuing." Images on social media showed a large plume of smoke rising above the city.
Health ministry spokesman Wahidullah Mayar said at least one person had been killed and 13 wounded so far.
Initial reports said the attack had been near a wedding hall that earlier hosted a campaign rally for Afghanistan's chief executive Abdullah Abdullah, one of the leading candidates running against Ghani on September 28.