At least five Iranian border guards were killed in a clash with an armed group trying to enter the country near the Pakistani border, Iranian state TV reported on Sunday.
The fighting took place in the town of Saravan in the south-eastern province of Sistan and Baluchistan, about 1,360km south-east of Tehran, it said.
Two border guards were wounded in the clash, the TV report added. The militants fled the area with casualties, it said, without elaborating.
Iran's intelligence minister said a "terrorist" group linked to Israel was arrested on the western borders of Iran on Sunday, according to the semi-official Nour news agency.
"A terrorist group associated with the Zionist regime which entered the country from the western borders was arrested," said Esmail Khatib.
The statement comes amid heightening tensions between Iran and its arch-enemy Israel over Tehran's nuclear programme.
State TV originally put the death toll among the security guards at six but later said there were five fatalities, AP reported.
No group has immediately claimed responsibility for the attack and Iranian authorities did not blame any group.
The area is one of the least developed parts of Iran. The relationship between the predominantly Sunni residents of the region and Iran’s Shiite theocracy has long been fraught.
On Thursday, the leaders of Pakistan and Iran inaugurated the first border market amid warmer relations between the two countries.
Located in the remote village of Pishin in Pakistan’s south-western Baluchistan province, the marketplace is the first of six to be constructed along the Pakistan-Iran border under a 2012 agreement.
Pakistan's Prime Minister Shahbaz Sharif and Iranian President Ebrahim Raisi also inaugurated an electricity transmission line, which will provide some of Pakistan’s remote regions with electricity from Iran.
