UPDATE 1-Maoist blast kills four during India president visit

(Updates death toll)

RAIPUR, India, Sept 29 (Reuters) - Suspected Maoist insurgents killed four policemen with a landmine blast on Monday in central India where the country's president Pratibha Patil was holidaying, police said.

Patil who was near a waterfall in Bastar, about 27 km (15 miles) from the blast site, was safe, police officer Girdhari Nayak said.

Bastar is in the central state of Chhattisgarh, one of several where Maoist rebels say they are fighting for the rights of poor farmers and landless labourers.

Three policemen were wounded in the latest explosion which took place in the forests of Bastar, Nayak said.

Thousands of people have been killed in the insurgency, which began in the late 1960s and stretches through the countryside across a swathe of eastern and central India.

Prime Minister Manmohan Singh has described the insurgency as the gravest threat to India's internal security. (Reporting by Sujeet Kumar; Editing by Bappa Majumdar and Sanjeev Miglani)