ADEN, Yemen, May 3 (Xinhua) -- At least four people were killed and eight others injured on Friday in a bomb blast in Yemen's southeastern province of Hadramout, a security official told Xinhua.

The local source, who asked to remain anonymous, said that a bomb planted by unknown elements on the roadside in al-Qatan district exploded and hit civilian cars and motorcycles, killing four people and injuring eight others in the area.

He said the initial reports indicated the bomb planted on the roadside was detonated with a remote-controlled device.

Three of the injured civilians were in critical condition and shifted directly to the intensive care unit at the district's hospital, local medical sources said.

Local residents said that security forces and rescue teams rushed to the bombing site and transferred the bodies and wounded to the district hospital.

The bomb blast also destroyed two motorcycles and a civilian vehicle, according to the local residents near the scene.

No group has so far claimed responsibility for the blast, but local security officials usually blame militants of the Yemen-based al-Qaida branch for masterminding such attacks targeting government forces and intelligence officers in Hadramout.

The government-controlled southeastern province of Hadramout and other areas in Yemen are witnessing growing activities of extremist organizations that take advantage of the conflicts in the impoverished country.