A court in the southern Indian state of Tamil Nadu has convicted 153 people in connection with a series of bombs that killed nearly 60 people in 1998.
LK Advani was the alleged target of the bombs
The man described as the mastermind of the plot, SA Basha, was among the guilty. Eight people were acquitted.
Nineteen bombs went off in the town of Coimbatore on 14 February 1998 just before Hindu nationalist leader LK Advani was due at an election rally.
Sentencing is due on 6 August, with 73 people facing death or life in jail.
Eighty others of those convicted face lesser sentences.
The BBC's TN Gopalan in Madras (Chennai) says many of those convicted on lesser charges are expected to be freed as they have spent so long on remand.
Five defendants are still awaiting verdicts.
In all 166 people faced charges of being involved in the blasts.
Basha, the founder of the banned radical Muslim group, Al-Umma, is the most high profile defendant to be convicted.
Another prominent defendant, Abdul Nasser Madani, the leader of the Kerala-based People's Democratic Party, was acquitted.
The 1998 bombings sparked clashes between Hindu and Muslim mobs in Coimbatore, some 2,413km (1,500 miles) south of Delhi.
The bombs went off about 800 metres from where Mr Advani was due to speak.
At the time, he was president of the Hindu nationalist Bharatiya Janata Party (BJP). He was not at the podium when the bombs went off because his flight had been delayed.
Coimbatore was the scene of Hindu-Muslim clashes in November 1997 after two men belonging to a radical Muslim group allegedly killed a Hindu policeman.
At least 17 people, most of them Muslims, died in the fighting.
Investigators said that the bomb blasts were part of a conspiracy to assassinate Mr Advani to avenge the killing of the Muslims.