NEW DELHI (AFP) - India's president has rejected mercy pleas from three men convicted of the 1991 assassination of then prime minister Rajiv Gandhi, paving the way for their execution, an official told AFP on Thursday. The appeal, sent to President Pratibha Patil by the men - Murugan, Santhan and Perarivalan, all known by single names - was their last hope of escaping the hangman's noose. All three belonged to Sri Lanka's LTTE group, which was accused of plotting the May 21, 1991 murder of Gandhi. Gandhi had become India's youngest ever prime minister after his mother, former premier Indira Gandhi, was assassinated in October 1984, and ruled until losing an election five years later.