Sorry for the very late reply, but yes, militants do use Ak-74 rifles. Maybe not so in the North (I couldn't find a source to back up my claims about J&K) but most definitely in the North East.
@mikhail
The following are excerpts from SATP.
June 3: State Police will seek custody of the six persons including four GNLA militants, who were arrested by the Assam Police along with a huge consignment of arms and ammunition from Gorchuk area of Guwahati on June 2, DGP N Ramachandran said . Four GNLA militants include one Pintu Marak, who is the brother-in-law of GNLA Commander-in-Chief, Sohan D Shira .
The consignment of arms and ammunition included one AK 74 assault rifle, one Berretta .32 pistol, 25 shells, 400 rounds of AK 74 ammunition, 500 rounds of 9 mm pistol ammunition, 20 rounds of ammunition of .32 Berretta pistol.
June 2: SFs arrested four GNLA militants including Pintu Marak, brother-in-law of GNLA 'commander-in-chief' Sohan D Shira, and two Nagaland-based arms smugglers from the Guwahati city's Tetelia area.
SFs recovered one AK-74 (grenade launcher) rifle, 25 grenades, one Barrette pistol and more than 900 live ammunition from their possession."The militants confessed that the consignment was procured from Myanmar and was being taken to Garo Hills through Nagaland and Assam. The weapons were concealed in secret chambers built inside the vehicle," Guwahati SSP Apurba Jibon Barua informed the media.
The ASEAN smuggling route makes it possible for the millitants to have access to quite a vast spread of weapons. It is quite common to find the American M-4s, Uzi and even the M-21/24 sniper rifles. In some cases, these rifles are found to be imported directly from the US.
If you want I can provide further links. But I trust it should be easy to make a google search.
Garo National Liberation Army (GNLA)