Three civilians have been killed in a suicide car bomb attack outside an army base in southern Afghanistan, officials have said.

Four Afghan soldiers were also injured in the explosion, which occurred in the Shahjoy district of Zabul province on Friday, Gulab Shah Alikhil, the provincial vice-governor, said.

"The driver of a vehicle blew himself up in front of the [Afghan army] base, killing three civilians who were employees queueing to enter. Four soldiers were also wounded in the explosion," he said.

There have been no claims of responsibility for the attack, but the explosion comes after a series of bombings by fighters linked to the Taliban, which is leading the ongoing insurgency against the Afghan government.

Afghan and international forces are frequently targeted in gun and bomb attacks, but civilians are often the victims.

Resurgent Taliban

The latest attack came a day after four fighters were killed in a shootout by Afghan and international troops in northeastern Kapisa province, according to a coalition statement.

The clashes broke out as Afghan and coalition forces targeted the Hizb-e-Islami Gulbuddin network.

"The force detained three suspected militants," the statement read.

Forces loyal to the Taliban, which was in power in Afghanistan between 1996 and 2001, have been resurgent in recent months, particularly in the south of the country.

Nearly 70,000 soldiers from the US and the Nato military alliance are the country fighting alongside government forces against the Taliban.