At least 11 Iranian police officers were killed in a jihadist-claimed attack on a police station in the southeastern province of Sistan-Baluchistan, an official told state television on Friday.
"In the terrorist attack on the police headquarters in the town of Rask, 11 policemen were killed, and others were wounded," said Alireza Marhamati, deputy governor of the province.
A number of assailants were also killed in a shootout that ensued with the security forces, the television channel reported.
The attack, which occurred around midnight, was one of the deadliest in years for the region close to Iran's border with Afghanistan and Pakistan.
It was claimed by the Sunni jihadist Jaish al-Adl (Army of Justice) group, the TV report said. Jaish al-Adl was formed in 2012 and is blacklisted by Iran as a "terrorist" group.
Unrest in impoverished Sistan-Baluchistan province -- which also borders Afghanistan -- has involved drugs-smuggling gangs, rebels from the Baluchi minority and Sunni Muslim extremists.
Similar attacks have previously occurred, including on July 23 when four policemen were killed while on patrol.
That came two weeks after two policemen and four assailants were killed in a shootout in the province claimed by Jaish al-Adl group.
In May, five Iranian border guards died in clashes with an armed group in Saravan southeast of Zahedan, the provincial capital of Sistan-Baluchistan.
State media reported at the time that the attack was carried out by "a terrorist group that was seeking to infiltrate the country" but whose members "fled the scene after suffering injuries".
In late May, IRNA quoted a police official, Qassem Rezaee, as saying "Taliban forces" had shot at an Iranian police station in Sistan-Baluchistan, a drought-parched region which also borders Afghanistan. The two countries have been arguing over water rights.
Zahedan, one of the few Sunni-majority cities in predominantly Shiite Iran, was also the scene of months-long deadly protests that erupted in September last year over the alleged rape of a teenage girl by a police officer.