A suicide bomber blew himself up at a wake in southern Yemen on Saturday night, killing more than 45 people and wounding at least 41, the interior ministry said.
The ministry expected the death toll to rise.
While no group immediately claimed responsibility for the attack in the town of Jaar in Abyan province, suspicion fell on al Qaeda which vowed to retaliate against tribesmen who fought alongside the government to uproot it from the region.
In June, the Yemeni military, with help from pro-government fighters, recaptured Jaar and the neighboring Zinjibar from al Qaeda militants. After it was forced out, the group said it would target those who had cooperated with the military.
In the Saturday incident, the bomber blew himself up while mourners were paying condolences to a pro-government fighter whose uncle had died. The attacker entered the gathering claiming to be a friend of the fighter, and then detonated explosives, officials said.
Kidnappings and violence in Yemen have become increasingly common in recent years, especially since last year's uprising that eventually ended President Ali Abdullah Saleh's 32-year rule in February.
Most of the violence have been blamed on affiliates of al Qaeda in the Arabian Peninsula, including the deadliest attack ever on Yemeni troops in May, when a massive suicide bombing killed more than 100 soldiers and injured 220 others.