The bill, tabled by President Vladimir Putin, is a follow-up on the Kremlin's offer of a fair trial for cooperative militants in Chechnya and other parts of the restive North Caucasus region. It was made after the killing of terrorist No.1 Shamil Basayev in July, and was initially valid until August 1, with the deadline later extended to September 30.
A senior MP said Monday the amnesty covered those who fought against federal forces in illegal armed formations.
"The amnesty also applies to military servicemen who committed crimes during the counterterrorism operation," said Pavel Krasheninnikov, chairman of the State Duma's civil, criminal, arbitral and procedural law committee, and a former justice minister.
But he said the amnesty did not extend to persons who committed grave crimes, including the theft or illegal sale of weapons.
He also said the amnesty did not cover foreigners and stateless persons.
Earlier this month, Russian security authorities said more than 200 militants had accepted the surrender offer since its announcement on July 15, most of them in Chechnya.