KABUL — U.S. Marines and Afghan troops today launched the first offensive since President Barack Obama announced an American troop surge, striking against Taliban communications and supply lines in a southern insurgent stronghold, a military spokesman said.

Hundreds of troops from the 3rd Battalion, 4th Marines and the Marine reconnaissance unit Task Force Raider were dropped by helicopter and MV-22 Osprey aircraft behind Taliban lines in the northern end of the Now Zad Valley of Helmand province, scene of heavy fighting last summer, according to Marine spokesman Maj. William Pelletier.

A second, larger force pushed northward from the Marines' Forward Operating Base in the town of Now Zad, Pelletier said. Combat engineers were forcing a corridor through Taliban minefields with armored steamrollers and explosives, Pelletier said.

In all, about 1,000 Marines as well as Afghan troops were taking part in the operation, known as "Cobra's Anger," he said.

There were no reports of NATO casualties. The spokesman for the Afghan governor of Helmand province, Daood Ahmadi, said the bodies of four slain Taliban had been recovered.

Ahmadi said 150 Afghan troops were taking part in the operation, which had located more than 300 mines and roadside bombs by the evening.