Three days of mourning began in the Iranian province of Sistan-Baluchestan on Monday, after dozens of people were killed in a militant attack a day earlier, state media reported.
A man carrying explosives blew himself up Sunday as participants headed to a conference between Shia and Sunni groups in southeastern Iran, killing at least 42, state-run Press TV reported.
The blast in the city of Sarbaz, in Sistan-Baluchestan, wounded 28 others, the semi-official Fars news agency said.
Among those killed were five senior officers of Iran's elite Revolutionary Guard Corps, Fars said.
Various media outlets offered conflicting figures for the number of dead and wounded, CNN reports.
On Sunday, state media said a local rebel Sunni group called Jundollah (God's soldiers) claimed responsibility for the attack, which also wounded many people ahead of a meeting with tribal chiefs in Sistan-Baluchestan province.
The southeastern province is the scene of frequent clashes between security forces, ethnic Baluch Sunni insurgents and heavily-armed drug traffickers.
Jundollah, which accuses Iran's Shi'ite-led government of discrimination against Sunnis in the remote desert region, has been blamed for many deadly incidents over the last few years, Reuters informs.