Maoist highway ambushes in the first week after Tihar indicate a dramatic shift in tactics by the rebels.

By blocking remote stretches of highways with trees, they lure troops out of their barracks and ambush them. In four attacks in western and central Nepal on Tuesday and Wednesday, 19 soldiers and police were killed and weapons looted.

At Agaiya on the East-West Highway, police trucks are still smouldering three days after six soldiers were killed. The highway is cratered and trees used for barricades litter the road. Buses and cars are plying again after three days, but the faces of stranded passengers wear a haunted look. There are no security forces in sight.

In a brief but fierce firefight at Khairi Khola near Kusma on Wednesday, eight APF personnel were killed. The police had taken cover on the side of the road, and were ambushed by hundreds of Maoists who ran away before a nearby army contingent arrived.

The army says the rebels have resorted to these "hit-and-run" attacks because they can't mount big raids on military bases anymore. The army has also launched pre-emptive airborne assaults in the Maoist heartland in the midwest after Dasain.

"We had intelligence they were planning a big attack, but we have been dispersing them," said one source. "That is why they are forcing our security patrols to respond to blockages on the highways."

If the rebel plan is to get the soldiers out of the security of their barracks, it is working brilliantly. "It is known as a tactical trap," explains military strategist Indrajit Rai, a retired Indian military officer. "When the vehicle hits the mine, the soldiers are distracted and in shock, that is when they are ambushed."

In the Krishnabhir attack on Tuesday (see Divided, they stand) hundreds of Maoists ambushed an army convoy after setting off several land mines along the Prithbi Highway. Rai says the Maoists need guns and ammunition since their supply lines from India have been disrupted. "They also need to arm new recruits," he adds.

The Maoist offensive also indicates that they have abandoned the political option for now. "They failed to mobilise the people through ideological indoctrination, so they are on full military mode," says political analyst, Dhruba Kumar. He says the army should have expected this, and blames the high casualty on poor planning. "The security forces need to do much more work to improve intelligence," he adds.

The army says it has been able to penetrate rebel cells, especially in eastern and central Nepal (see Divided, they stand) and credit better intelligence for the Maoists' inability to launch any major frontal assault since Beni in February. The army has Indian-built mine-protected vehicles, but these are designed to withstand explosions from below, not roadside bombs planted on slopes that come from the side.

(Additional reporting by Navin Singh Khadka)