India\'s president urged outlawed Maoist guerrillas on Friday to \"leave violence\" and accept the government\'s offer of peace talks. Pratibha Patil\'s appeal followed a string of Maoist-led attacks which left 18 security personnel dead earlier this month in the insurgency-riven central Indian state of Chhattisgarh. \"I appeal to the Maoists and others involved in violence, to leave violence and engage in talks,\" Patil said in an address to the legislature in the state capital, Raipur. Patil\'s comments were the second presidential appeal since last August to the guerrillas, who are active in 20 of India\'s 29 states. \"Violence and killings are condemnable offences which cannot be accepted by any civilised society... They should join the mainstream and allow the development of the tribals in this country,\" the president added. Tribal groups and many rural areas have been left behind by the country\'s economic development, and the poverty and discontent is seen as a major source of the Maoist uprising which kicked off in 1967. Chhattisgarh is in the eye of Maoist-led violence, which peaked with the massacre of 76 policemen in a brutal attack in April last year. The guerrillas have also stepped up attacks elsewhere in response to the Indian government\'s \"Operation Green Hunt\" offensive launched in 2009 in Maoist-hit areas across north and eastern India. The Maoists also feed off police brutality and government corruption, and are strongest in the poorest and most deprived areas of India, many of which are rich in natural resources. Prime Minister Manmohan Singh has identified Maoist insurgency as the number one threat to domestic security.