The Supreme Court has upheld the conviction of actor Sanjay Dutt in the 1993 Mumbai blasts case but reduced the six-year jail term by the TADA (Terrorist and Disruptive Activities) court to five years.

Times of India reported the actor has four weeks to surrender and according to the court the circumstances and nature of the offence was so serious that Dutt cannot be released on probation.

The apex court said it agreed with TADA court's decision to acquit Dutt of terror charges but "offences under the Arms Act were clearly made out for possessing and later destroying weapons of prohibited calibre."

Dutt, who has already served nearly 18 months in jail, will now have to return to jail and serve the remaining term.

He would not be able to shoot pictures during the remaining three-and-a-half years of prison term.

Dutt was sentenced to six years imprisonment for illegal possession of firearms acquired from terrorist acquaintances who were responsible for the 1993 Mumbai bomb blasts on July 31, 2007.

He was granted bail by the apex court on Nov 27, 2007.

A total of 257 persons were killed and 713 others injured when a series of 13 coordinated explosions shattered the metropolis on March 12, 1993.

The blasts occurred at 12 places including the Bombay Stock Exchange building, Air-India Building at Nariman Point, Worli opposite Century Bazaar, Hotels Sea Rock, and Juhu Centaur.