"Their goal is to increase a base to expand into the CIS (ex-Soviet Commonwealth of Independent States) territory."

The expansion into the ex-Soviet countries "will be done by militants who are citizens of Central Asian republics with experience of warfare as members of terrorist groups," Bortnikov said.

The comments come on the heels of an attack Wednesday on a border post in Tajikistan which officials blamed on members of the IS group who crossed over from Afghanistan.

Tajikistan authorities said 15 attackers were killed and four detained, while a soldier and a policeman were also killed.

Tajikistan and other ex-Soviet countries of Central Asia have been major sources of recruits for militants group in Syria and Iraq, with some travelling there from Russia where many work as labour migrants.

IS propaganda outlets have referred to territories in Central Asia as 'wilayas', or provinces.

IS militants have also claimed several attacks in Tajikistan, including a hit-and-run that killed four Western tourists on a cycling trip last summer.—AFP