At least four people have been killed after a rocket-propelled grenade was fired into a crowd during a religious gathering in Yemen.
10 others were injured outside a celebration hall in the capital Sanaa.
The attack happened as an important day for Shi-ite
Muslims, the holy day of Ashura, was being observed.
The occasion, for the climax of the mourning month of Muharram, was being marked for the first time in Yemen.
There have been regular tensions between extremist Salafists, who are Sunni Muslims, and Shiite tribesmen known as Hawthis.
Nearly 200 people died in fighting late last year in northern Saada province.
Yemen regularly sees attacks by al-Qaeda as well as civil unrest following its own Arab Spring uprising.