Source of explosions and gunfire in Western Iran is still unknown.

Missile being fired by Iranian army in 2016. Image Credit: AP
Last Saturday night, social media was flooded with reports from journalists and citizens regarding series of loud explosions and gunfire in Western Iran, around the cities of Kermanshah and Hamedan.
There were some reports that suggested that the Iranian revolutionary guard launched air defence drills, but the weather was overcast with snow and rain, and so the chance that it was a military drill is close to nil.
One source which could not be verified for its authenticity released a video that indicates that the sound resembles very much like an anti-aircraft gun fire, and a person mentions that explosions were heard, suggesting that it might have been an aerial attack on Iranian infrastructure. Regardless of this, there have been no reports of aircraft activity in the region, but there is a source which said that one anti-aircraft missile was fired, and an explosion was heard close to a military base.
Given the recent tensions in the regarding Iranian’s nuclear weapons, one could not rule out an attack on Iranian soil. It would not be the first time, as Iranian military bases and nuclear sites have often been targeted by aerial or sabotage attacks.