TEHRAN, Iran (AP) — Six Iranian border guards were killed in a clash with an unknown armed group trying to enter the country near the Pakistani border, state TV reported Sunday.

The fighting happened in the town of Saravan in the southeastern province of Sistan and Baluchistan, some 1,360 kilometers (850 miles) southeast of the capital Tehran. The report said the militants fled the area with casualties, but did not elaborate.

TV also said two border guards were wounded in the clash. It did not blame the attack on any group and no group immediately claimed responsibility. There were no additional details.

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 top leaders of Pakistan and Iran inaugurated the first border market as relations warm between the two countries.

Located in the remote village of Pashin in Pakistan’s southwestern Baluchistan province, the marketplace is the first of six to be constructed along the Pakistan-Iran border under a 2012 agreement signed by the two sides.

Pakistani 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 Iranian electricity.