MOSCOW: Security officers shot dead three militants on Sunday in Russia's volatile North Caucasus republic of Dagestan, the epicentre of an Islamist insurgency, local media reported.

Russia has tightened security in the surrounding region less than a year ahead of the 2014 Winter Olympics, which it is planning to host on the western side of the Caucasus mountains, 1,000 km (620 miles) from Dagestan.

RIa news agency said the militants were hiding in a wood and opened fire on security officers searching the area in the early hours of Sunday morning.

"Three militants are killed. There are no injured among the law enforcement officials," another agency, Interfax quoted the regional arm of Russia's top criminal investigative agency as saying.

Moscow is struggling to quell the persistent Islamist insurgency more than a decade after it fought two separatist wars in the adjacent republic of Chechnya.

Rights groups say the revolt is driven by a volatile mix of religion, corruption and grievances against the strong-arm tactics of some local leaders against suspected militants and their families.

President Vladimir Putin, who rose to prominence by crushing the Chechen rebellion, has ordered Russian security forces to be on high alert to secure the 2014 Winter Olympics, due to be held in the Black Sea resort of Sochi in Krasnodar region, separated from the North Caucasus by three small states.