Fourteen Iranian border guards were killed and three others captured by "bandits" on the southeastern frontier with Pakistan overnight, Iranian media reported on Saturday.
In response, the Iranian judiciary executed 16 people it said were elements of "terrorist" groups, according to the ISNA news agency. There were no further details of who they were or whether or when they had been tried.
"These individuals were executed this Saturday morning in response to the terrorist action of last evening at (provincial capital) Saravan and the martyrdom of the border guards," Zahedan public prosecutor Mohammad Marzieh said, according to ISNA.
The reports gave no details on the identity of the gunmen who had killed the border guards, but the area has a history of unrest, with the mainly Sunni Muslim population complaining of discrimination by Iran's Shi'ite Muslim authorities.
Sunni Muslim militant group Jundollah, which Iran says is linked to al Qaeda, has claimed a number of attacks and kidnappings since 2003, including a 2010 suicide bombing that killed dozens of people at a Shi'ite mosque.
Iranian security forces have also fought drug traffickers in the region that borders Pakistan and Afghanistan.
Iranian media quoted officials as saying "bandits" attacked an official post near the Pakistani border on Friday evening.
"We want Pakistani officials to take steps regarding more serious and stronger control of their borders than in the past," Deputy Interior Minister Ali Abdollahi told ISNA.
Abdollahi said 14 border guards were killed, six wounded, and three were seized by the attackers. He said Iran was working to free the captured guards.