Launching the country's biggest ever anti-Maoist offensive, security forces on Tuesday adopted a new strategy of guerilla warfare in the hunt for naxals in the dense forests of Orissa where additional paramilitary personnel have been rushed to join the long haul operation.

Backed by helicopters and sniffer dogs, over 1,000 policemen intensified their search for the maoists involved in the Nayagarh attack in which 14 policemen and one civilian were killed last Friday after failing to locate them in Gosmah forest, official sources said. Fresh reinforcements of 500 Central Reserve Police Force were rushed by the Centre.

"Besides using Air Force choppers to spot the ultras inside jungles, the security forces deployed a large number of trained dogs," said a senior officer engaged in the four-day-old combing operation.

Suspecting the presence of landmines and claymore mines in the jungles, the security forces were using sniffer dogs to locate the ultras suspected to be hiding in the caves of Singhasini hills near Buguda in Ganjam district.

The change of strategy to nab the ultras was believed to have been influenced by the death of three prominent members of the Special Operation Group, including assistant commandant Pramod Kumar Satpathy, during the combing operation.

"Instead of chasing the ultras into jungles, the force will now wait for the enemies to surface as per the new strategy," an officer said.

"We do not want to sacrifice more personnel by directly confronting the ultras and raiding their hideouts. The enemies were obviously in an advantageous position inside the forests. They knew the routes and were well acquainted with the terrain," a police official engaged in the operation said.

The officer said moonlight had helped the ultras to slip from their hideouts in Gosmah forest which was encircled by the security personnel. "It was easy for the ultras to escape taking advantage of their knowledge of forest routes," the officer said.

Personnel of the Orissa police, SOG, CRPF and Greyhound from Andhra Pradesh were also carrying out the operation in the jungles of Ganjam, Kandhamal and Gajapati districts adjoining Nayagarh district.

While Kandhamal superintendent of police Nikhil Kanodia was leading a group in Daringibadi area, southern range DIG R P Koche was heading another group.

"Even district magistrates of several districts were asked to help in the combing operation, said to be the biggest ever anti-Maoist operation in the country," claimed a senior home department official.

Sources said the combing operation was likely to continue for a long period.

Meanwhile, concerned over a spate of naxal attacks in some states, the home ministry is seriously considering a proposal to raise fresh India Reserve Battations and CRPF Battalions.

A high-level meeting, chaired by home minister Shivraj Patil discussed the proposal with the Union home secretary, special secretary (internal security) and heads of central para-military forces.