Sadan warned that the continuous attacks launched by AQAP against Shiite rebels "could indulge the whole region into a sectarian conflict, especially with the existence of hatred- ignited long differences and disputes between Sunni and Shiite sects."

The Shiite rebels, however, played down these fears, arguing that "AQAP is no more than an intelligence tool controlled by the United States."

The spokesman of Houthi Shiite rebels, Mohammed Abdul Salam, told Xinhua that the Houthi group "would not allow the fulfillment of any intelligence plan plotting to get Yemen into a sectarian conflict."

In its 2010 report about the religious freedom in Yemen, the U.S. State Department also took notice of "the increasing hatred and discrimination between the followers of Shiites and Sunnis in northern provinces of Yemen."

"The growing religious and political extremism of Shiite rebels was behind escalating violence between the Shiite and Sunni communities in north Yemen," said the report which was issued in October.