The trio, comprising of a suicide bomber and two gunmen, targeted the parliament on Tuesday, Oct 19.
According to RIA news agency, the suicide bomber first detonated explosives outside the parliament building, following which the gunmen barged in.
They then engaged in a gun battle with guards around the building, the news agency report said.
As per Interfax news agency inputs, the shooting is still on.
Islamist insurgency continues to grow in the North Caucasus region. There has been a slew of shooting and bomings reported from Chechnya recently.
The insurgency and violence continues even after the Kremlin had declared victory in its battle with Chechen separatists.