Iran has executed 16 rebels following overnight clashes in which 14 border guards were killed close to the border with Pakistan, an official has said.

An Iranian prosecutor said that authorities had executed 16 "terrorists" in the country's Sistan-Baluchestan province, in retaliation for the killings.

"These individuals were executed this Saturday morning in response to the terrorist action of last evening at Saravan and the martyrdom of the border guards," he said, quoted by Iranian state television.

He gave no details of any trial proceedings.

Iran's state TV reported earlier on Saturday that at least 14 Iranian border guards were killed in clashes with "armed bandits" without providing any details on the identity of the group behind the killings.

Details on the number of border guards killed were also unclear, with the Reuters news agency reporting 20 killed, and Iranian State TV suggesting the number to be closer to 17.

Al Jazeera's Soraya Lennie, reporting from Tehran, said the Iranian government was blaming a separatist group, known as Jaish Ul Adl (Party of Justice), for the attack on its border guards.

Our correspondent said this "relative new group" was vehemently anti-Shia and the Iranian government had in the past pressured the Pakistani government to crack down on the group's activities.

The area also has a history of unrest, with the mainly Sunni Muslim population complaining of discrimination at the hands of Iran's Shia Muslim authorities.

Security forces have also fought drug traffickers before in the border region with Pakistan and Afghanistan.

IRNA quoted an unnamed official saying the fighting took place in the southeast Sistan-Baluchistan province and the exact number of dead had not been confirmed.