Sughd Province police chief Sharif Nazarov told journalists that six IMU members were arrested last week in the region that borders Uzbekistan.
Nazarov added that two assailants who killed a policeman and wounded his partner in the area on January 14 have also been identified as IMU members.
Nazarov refused to reveal any names, citing security reasons.
The IMU, which says it wants to establish an Islamic caliphate in Central Asia, is believed to have links with the Taliban and Al-Qaeda.
It had been active in the region, but in recent years moved its operations to neighboring Afghanistan.