About six civilians were wounded Thursday morning in a roadside bombing in Yemen's southern province of Lahj, a provincial source told Xinhua.

"A small bus touched off an Improvised Explosive Device (IED) near a crowded public market in Yafea region in Lahj province. The explosion injured six people," the provincial police source said on condition of anonymity.

The security forces have cordoned off the area, and an investigation was underway. The target of the roadside bomb attack remained unknown, according to the source.

A local medic said anonymously that most of the injured were in critical conditions.

No group has claimed responsibility for the attack and government authorities have yet to comment.

Militants of the Yemen-based al-Qaida offshoot were blamed by the country's government for a series of assassinations and armed attacks, mostly in the country's southern regions.

The al-Qaida in the Arabian Peninsula, which emerged in January 2009, is considered the most strategic threat to the Yemeni government and neighboring oil-rich Saudi Arabia.