India's Maoist guerrillas on Tuesday threatened to kill the country's prime minister and ruling party leader in what analysts said was the most aggressive threat yet from an increasingly lethal and widespread insurgency. The warning comes a month after the government listed the Communist Party of India (Maoists) as a terrorist group, and Prime Minister Manmohan Singh declared them India's largest internal security threat. The Maoists targeted Singh and Congress party president Sonia Gandhi, and invoked the memory of the 1991 assassination of her husband, former Prime Minister Rajiv Gandhi, in a suicide blast blamed on Sri Lanka's now-defeated Tamil Tiger rebels. “Sonia Gandhi and Manmohan Singh have dared to ban the Maoists, little realizing that they would meet the fate of Rajiv Gandhi, who was killed by the LTTE (Liberation of Tamil Tigers Eelam),” a Maoist statement released in Hindi says. India blamed the LTTE for killing Gandhi as revenge after a 1987-1990 Indian peacekeeping mission to Sri Lanka turned sour. The statement, issued in the eastern state of Jharkand, also gave local Congress leaders a week to resign or “be taught a lesson”. Jharkand police and Congress officials said they were taking the threat seriously, while Singh's office had no comment. Sri Lanka crushed the LTTE in May after a 25-year war, in which the separatists had proved themselves ruthlessly efficient at killing politicians, police and other government officials to inspire fear, a tactic analysts say the Maoists have adopted. “It is the boldest statement ever issued by them,” said Colonel R. Hariharan, a Chennai-based security analyst who led military intelligence during India's peacekeeping mission to Sri Lanka. Earlier this month, Maoists ambushed and killed at least 29 police officers on patrol in the jungles, and counterinsurgency experts say police officers tackling the Maoists lack the proper training and equipment to be effective.