MAKHACHKALA, July 2 (RIA Novosti) - A traffic police officer who was shot in Russia's North Caucasus Republic of Daghestan died in hospital early on Thursday, an Interior Ministry spokesman said.

"A traffic police officer injured on Wednesday evening when a police car came under fire from unidentified assailants near the village of Shamkhal died in hospital in the early hours of Thursday," the source said.

At about 18:40 Moscow time (14:40 GMT) on Wednesday a group of unidentified attackers opened gunfire at a stationary traffic police car containing two officers on the Kavkaz Federal Highway, some 20 km north of the regional capital, Makhachkala. One of the officers died at the scene, the other was taken to hospital in critical condition.

Militant attacks and clashes remain common in Russia's North Caucasus, although the Kremlin campaign to fight separatists and terrorists in Chechnya has officially ended. Violence often spills over into nearby republics, in particular Ingushetia and Daghestan.

In a separate development, a sapper was killed in an explosion which occurred early on Thursday on a railway in Daghestan's Karabudakhkent district, to the south of Makhachkala.

The first explosion occurred on a rail track when a repair train was passing by. When bomb experts arrived at the scene, the second explosion occurred, killing the sapper.