Those killed were oil company workers who boarded a bus in Mazar-i-Sharif, according to a civilian official.
At least seven people have been killed in a roadside bomb attack in northern Afghanistan, according to officials, the latest attack in the violent country.
Those killed in the explosion at 7am (03:00 GMT) on Tuesday in the city of Mazar-i-Sharif included oil company workers on a bus, government officials said.
“The bomb was placed in a cart on the side of the road. It was blown up when the bus was arriving,” said Asif Waziri, of the Balkh police department in Mazar-i-Sharif.
The northern province of Balkh has one of the country’s dry ports in the town of Hairatan near the border with Uzbekistan, which has rail and road links to Central Asia.
It was not immediately clear who carried out the attack, which comes as the Taliban government promises to bring security to Afghanistan after years of war.
The Taliban government came to power in August last year when US-led foreign forces seized control of the country and ousted the group in 2001.
Last month, at least 19 people were killed and 24 others injured in an explosion at a school in Aybak, Samangan city, which is located near Balkh province.
In May, at least nine people were killed in a series of explosions in Mazar-i-Sharif, while two others were killed in a simultaneous attack on a mosque in the capital, Kabul.
ISIS (ISIS) – the main enemy of the Taliban in Afghanistan – claimed responsibility for the violence in Mazar-i-Sharif, but not for the explosion in Kabul.
Recent violence has included a bombing that killed four people at a mosque in Afghanistan’s Interior Ministry building in October.