An Afghan official said that 6 people were killed today, Tuesday, when an explosive device detonated targeting a bus in the city of Mazar-i-Sharif, the capital of Balkh Province, in the north of the country.

Al-Jazeera correspondent quoted the official as saying that 13 other people were injured in the attack, the motives behind which were not immediately known.

For its part, the Afghan police said that at least five people were killed in an explosion in a vehicle carrying employees of an oil company in Balkh province.

"An explosion occurred today in Balkh targeting a bus belonging to employees of an oil company," said police spokesman in the northern province of Balkh, Muhammad Asif Waziri, adding that at least four people were injured in the explosion, in addition to the dead.

There have been several attacks in urban centers in Afghanistan in the past few months, some of which have been claimed by the Islamic State group.