Sanaa, Yemen (CNN) -- Hundreds of Yemeni security forces deployed to the southwestern city of Rada Thursday after the leader of an al Qaeda-linked cell was killed by his older brother, sparking retaliatory attacks that also left the brother dead, security officials in the province told CNN.
Tareq al-Thahab headed a cell of al Qaeda in the Arabian Peninsula (AQAP) that recently took over Rada, in al-Baitha province, and declared it an Islamic emirate.
Three provincial security officials said he was killed by his brother, Hizam al-Thahab, who was apparently angry about the murders Wednesday of the regional head of the national election committee and four other officials accompanying him -- killings in which he believed his brother may have been involved. Hizam al-Thabab reportedly feared that the assassinations of the elections officials would bring reprisal killings against the powerful al-Thahab tribe.
Tribal sources told CNN that Tareq al-Thahab was killed inside a mosque where he and four followers were seeking shelter.
The defense ministry and the governor of al-Baitha confirmed his death.
Two hours later, militant loyalists of the AQAP cell bombarded the compound where Hizam al-Thahab was staying, killing him and injuring two other relatives.
Rada, a small town 170 km (105 miles) southeast of Sanaa, was taken over last month by militants led by Tareq al-Thahab, who announced the town an Islamic emirate. Eleven days after seizing the city, his fighters evacuated after reaching a deal with a government-led mediation committee to leave the town safely.
After the killing of Tareq al-Thahab and the apparent retaliatory murder of his brother, hundreds of security forces deployed to Rada Thursday morning and seven security checkpoints were set up.
"The situation is tense now and we are prepared for the worst," one security official, who is not authorized to talk to the media, told CNN.
"This was expected, but we are hoping that no escalation takes place in the province before the presidential elections next week," he added.
Tareq al-Thahab was the brother-in-law of American-Yemeni militant cleric Anwar al-Awlaki, who was killed in a U.S. drone strike last year. Al-Awlaki was married to al-Thahab's sister.
Yemen has been desperately trying to weaken terror militant groups after they succeeded in taking over large parts of the southern Abyan province last year.