Indian officials say three men convicted of the assassination of former prime minister Rajiv Gandhi 20 years ago will be hanged September 9.

President Pratibha Patil rejected the men's clemency petitions earlier this month.

Prison officials say the men have been informed about the date of the hanging.

A lawyer for the men told an Indian newspaper that he will seek a stay of the hangings and a set-aside of the death sentences.

The men were sentenced to death in 1999 for their part in the assassination, but had appealed to the president for mercy.

A total of 26 people were tried, convicted and sentenced to death in the case. However, India's Supreme Court subsequently changed the majority of the sentences to life in prison.

Gandhi was assassinated in 1991 as he campaigned in southern India for reelection. He was killed by a woman suicide bomber who exploded a bomb wrapped around her waist as she knelt to touch Gandhi's feet.

Soon after the assassination, the Tamil Tigers said they killed Gandhi to protest India's involvement in Sri Lanka's civil war.

Some information for this report was provided by AP, AFP and Reuters.