Five civilians and an Afghan army soldier were injured Monday morning in a bomb blast in the northern Afghan province of Balkh, an official said.

"Six wounded people including an army soldier were admitted to a provincial capital hospital in Mazar-i-Sharif city at around 11 a.m. local time Monday," a health official told Xinhua.

Earlier, a police spokesman in the northern Afghanistan, Lal Mohammad Ahmadzai, told Xinhua that three civilians were injured in the explosion caused by a sticky bomb attached to a bicycle near the building of provincial department of culture and information in the city, some 305 km north of the Afghan capital Kabul.

The obvious target of the attack was not clear and no group has claimed responsibility for the attack so far.

Violence has been on the rise since the Taliban insurgent group launched annual spring offensive on May 3.

Afghan security forces took full control of security in Balkh province, part of a security transition which started in July last year, and by the end of 2014 they are to be in charge across the country, allowing foreign combat troops to either leave or take on supportive roles.

Around 130,000-strong NATO-led coalition troops currently station in Afghanistan.

Under the US President Barack Obama's withdrawal plan, 10,000 US troops already pulled out of Afghanistan in 2011 and another 23,000 will return home by September this year.

At least 16 people were killed and 90 others, including two US soldiers with the coalition, were injured when Taliban carried out twin suicide bombings in Sayyidabad district in eastern Wardak province on Saturday.