SANAA, Aug. 8 (Xinhua) -- At least five Islamist Salafi Sunnis were killed in an ambush by Shiite Houthi rebels on Thursday in Yemen's northern province of Saada, tribal sources said.
Another nine Sunnis were seriously injured in the attack outside the Sunni-control small town of Dammaj, the sources told Xinhua by phone.
"Armed Houthis at their newly established checkpoint fired at the armless Sunni men after they passed the checkpoint," they said.
Following the attack, tension in the province escalated. In recent years, the conflicts between Sunnis and the Shiite Houthi rebels in the Yemeni northern regions have taken place.
Saada, bordering top oil exporter Saudi Arabia, is the stronghold of the Shiite rebels who have been controlling most of the province since they signed a cease-fire deal with the Yemeni government in August 2010, which ended an on-and-off war since 2004.
The Shiite then got involved in sectarian clashes with local armed Sunni tribesmen, which rocked the northern regions and forced thousands of Sunni local residents to flee the conflict to remote areas.
The well-armed Houthis have agreed to join a UN-sponsored reconciliation national dialogue planned by Yemeni President Abd- Rabbu Mansour Hadi which started in March and scheduled to run for six months.
Rival Islamic militants exploited security vacuum during Yemen' s political upheaval in 2011 and captured swaths of remote lands.