BISHKEK (Reuters) - Kyrgyz and Tajik border guards exchanged fire on Thursday amid a standoff over a blocked road, a fresh outbreak of violence between the ex-Soviet neighbours after a similar frontier clash killed dozens last year.

       The border between the two countries, both of which host Russian military bases and are closely allied with Moscow, is poorly demarcated.

       Kyrgyz authorities said Tajik citizens had blocked a road between provincial centre Batken and the Kyrgyz village of Isfana. Border guards on both sides managed to get the road unblocked, but then fighting broke out.

       The provincial government said no casualties had been reported. Tajikistan's border guard service had no immediate comment. An official from the local administration of the Tajik border town of Isfara wrote on Facebook that it was the Kyrgyz side which blocked the road.

       At least 49 people were killed in fighting between the two predominantly Muslim nations last April which escalated from a similar border clash.

       (Reporting by Olga Dzyubenko; Additional reporting by Nazarali Pirnazarov in Dushanbe; Writing by Olzhas Auyezov; Editing by Nick Macfie)