NEW DELHI: Bollywood actor Sanjay Dutt will have to undergo a jail term of three years and six months after the Supreme Court on Thursday upheld his conviction in the 1993 Mumbai serial blasts case which it said was organised by underworld don Dawood Ibrahim and others with the involvement of Pakistan's ISI.

However, the apex court reduced to five years the six year jail term awarded to him by a designated TADA court in 2006, ruling out his release on probation because the "nature" of his offence was "serious".

53-year-old Dutt, son of the late Sunil Dutt and Nargis, has already spent one and half years in jail and was out on bail. Sunil Dutt was a long standing Congressman and was a Union minister.

Dutt was convicted by the TADA court for illegal possession of a 9 mm pistol and a AK-56 rifle which was part of the consignment of weapons and explosives brought to India for the coordinated serial blasts that killed 257 people and injured over 700.

Bringing to a closure the appeals by the convicts and the state in the case, a bench of justices P Sathasivam and B S Chauhan upheld the death sentence of Yakub Abdul Razak Memon, brother of one of the absconding main conspirators Tiger Memon and life sentences of 16 of the 18 convicts.

The death sentence of 10 others was commuted to life sentence by the court which directed that they will remain in prison till death.

The life sentence of one Ashrafur Rehman Azimulla was reduced to 10 years while Imtiyaz Yunusmiya Ghavte was set free by reducing the sentence to jail term already undergone.

"The circumstances and the nature of the offence is so serious that we are of the view that he (Sanjay Dutt) cannot take the benefit of provisions of the Probation of Offenders Act to release him on probation," the bench said.

"We reduce the punishment of six years to minimum of five years under the Arms Act," the bench said and directed him to surrender within four weeks.

Sanjay Dutt's lawyer Satish Maneshinde said he has spoken to the actor who told him that he was strong enough to go through whatever the court has asked him to undergo.

"He has accepted the judgement, he said adding "he will go through the verdict and will consider all the legal recourses available to him".

The apex court concurred with the conclusion arrived at by the designated TADA court saying that it had adopted the "correct procedure" while awarding the sentence to Dutt.

"We are in agreement with conclusion arrived at by the designated TADA court that had rejected the arguments of the appellant Sanjay Dutt," the bench said.

"We are of the view that the trial court adopted the correct procedure and the decision arrived at by it was correct," it said and directed Dutt to surrender within four weeks from today.

According to the CBI, RDX had come from Pakistan in boats and had landed in Dighy and Shekhadi coasts in Raigad district in January and February 1993. Besides, weapons had also landed and were collected by Tiger's men. One of the weapons was given to actor Sanjay Dutt by Bollywood filmmakers Samir Hingora and Hanif Kadawala.

The apex court modified the nine year jail term awarded by TADA court to Hingora to the jail term already undergone.

Hingora had supplied AK-56 rifles, magazines, cartridges and hand grenades, which were part of the illegal consignment to be used in the blasts, at Dutt's Pali Hill residence and has spent six and half years in jail.

Kadawala was shot dead in February 2001 by two unindentified men during the trial of the case.

The apex court upheld the five-year jail term awarded to Zaibunnisa Anwar Kazi, who also was found guilty of storing AK-56 rifles and hand grenades.

The court also upheld the conviction and five-year sentence of Yusuf Mohsin Nulwalla, a close friend of Dutt, who was held guilty of destroying the weapons which were kept at Dutt's house.

The punishment of two-year jail term of Kersi Bapuji Adjania, who was also sentenced for destroying weapons in Dutt's possession, was also upheld.

According to CBI, Nulwalla had picked up the weapons from Dutt's house and took them to Adjania and then destroyed them.

The court, however, dismissed Maharashtra government's appeal against the acquittal of Ajai Yash Prakash Marwah who was charged by the probe agency of keeping the pistol recovered from Dutt's residence while other weapons were destroyed by convicts Nulwalla and Hingora.