At least 17 people died after Islamic State (IS) group militants attacked a checkpost on Tajikistan's border with Uzbekistan, Tajik authorities said.
The 20 fighters launched their attack at 03:00 local time (22:00 GMT), killing a border guard and a police officer but losing 15 men in the ensuing firefight, they said.
IS has not confirmed its involvement.
Police have closed roads in the area, while Uzbek border authorities are reportedly watching the situation.
Five of the militants were captured after the attack, which took place 60km (37 miles) south-west of the Tajik capital Dushanbe.
Photographs from the scene released by Tajikistan's interior ministry show bodies - some badly burned - lying around a number of cars.
The state-run Khovar news agency said the attackers crossed into the country from Afghanistan on 3 November.
The attack came a day after Tajikistan and Uzbekistan reportedly agreed to settle a long-running border dispute, with the aim of signing a deal before the end of the year.
IS has claimed several attacks in Tajikistan in the past.