KABUL - NATO forces are putting more trained Afghan troops on the front lines and plan "rolling operations'' against Taliban insurgents who are intensifying their attacks, but remain unable to mount territory-seizing offensives, military officers say.

Still, there's little prospect the suffering of combatants or civilians will abate. After a bloody 2006, violence has escalated again, leaving more than 1,000 people dead in the first four months of 2007, according to statistics compiled by The Associated Press.

In the field and at NATO headquarters, there's two-fold optimism for the military campaign in the months ahead: that large-scale operations against the Taliban's southern strongholds have blunted what appeared to be a drive to seize vital terrain, and that the Afghan National Army is crystalizing into an effective fighting force.

"We're cynical about the so-called spring offensive. It may happen, but so far we haven't seen one,'' says British Squadron Leader David Marsh, NATO's spokesman in the south. "We've had a winter campaign to knock off what they might be able to do in the spring.''

Yet, in a sign the conflict is deepening, the casualty figures on all sides for the first four months of the year are sharply up.

With the annual fighting season scarcely begun, at least 320 Afghan civilians and military and about 680 militants have been killed so far in 2007, according to figures compiled by AP from Afghan, NATO and U.S. officials.

That combined toll of 1,000 is more than double the total fatalities for the first four months of 2006 -- which saw the deadliest spate of fighting in Afghanistan since U.S.-led forces ousted the Taliban regime in late 2001.

The number of militants killed has more than tripled in 2007, and combined casualties among civilians and Afghan security forces have doubled. The number of coalition and NATO soldiers killed has risen to 39, from 15 during the same period of 2006. Deadly bombings happen every day. Last week, a roadside bomb hit a UN convoy in the southern city of Kandahar, killing four Nepalese guards.

On Wednesday, a bombing killed seven Afghan soldiers in eastern Paktika province, the latest in a string of attacks that have inflicted multiple casualties on security forces.

There have been at least 39 suicide attacks this year, a three-fold increase over the same period in 2006, according to the NGO Safety Office, which advises relief groups on security.

Last year's ominous upsurge in Taliban strength prompted calls to increase U.S. and NATO troops, which are expected to total 52,000 by summer's end from the current 47,000, NATO spokesman Col. Tom Collins said. That compares with about 32,000 at the start of 2006.

Forces, he said, would be fighting a "rolling series of operations,'' not necessarily just in prime Taliban strongholds like Kandahar and Helmand provinces, but in other areas where the militants were concentrated but had not yet been confronted.

Last year, it became apparent that militants were able to control tracts of southern Afghanistan and wanted to expand their domain. NATO had to mount a major offensive that inflicted major losses on hundreds of Taliban fighters threatening the city of Kandahar.