KANDAHAR, Afghanistan, June 20 (Xinhua) -- Two civilians were killed and two civilians and two policemen wounded in a bomb attack in Afghanistan's southern province of Kandahar overnight, provincial government spokesman said Wednesday.

"The blast occurred roughly at 08:30 p.m. local time Tuesday in Spin Boldak district when a sticky bomb attached to a vehicle was detonated at a police checkpoint, killing two civilians aboard the vehicle and injuring two civilians and two police officers of the checkpoint," spokesman Daud Ahmadi told Xinhua.

The injured were shifted to the district hospital.

Security situation has been improving in Kandahar, the former stronghold of Taliban, over the last months, as security forces have conducted search and cordon operations across the province. But the militants attack government interests in the province from time to time.