KABUL, Afghanistan - Afghan and U.S.-led coalition forces arrested a suspected bomb expert and five other terror suspects Wednesday in eastern Afghanistan, as NATO forces in the south fought Taliban militants in the second day of the alliance's largest-ever offensive in Afghanistan.

The U.S.-led coalition had information indicating "a suspected terrorist with strong ties to al-Qaeda" and to a group that helped militants along Afghanistan's border region was inside an eastern Afghan compound near Jalalabad, it said.

"The suspected terrorist was a (bomb-making) expert and logistics officer for the Tora Bora Front, which facilitates the movement of fighters from Pakistan to Afghanistan," the U.S. said. No shots were fired and no one was hurt during the raid.

In southern Afghanistan's Helmand province, meanwhile, some 5,500 NATO and Afghan soldiers fought Taliban militants in the second day of NATO's largest-ever offensive here.

NATO hopes the operation can help establish security in a lawless region ruled by a Taliban shadow government and drug traffickers. Helmand is the world's biggest poppy-growing region.

"We've established a presence and in some areas it's a heavy presence, and we're trying to disrupt the Taliban's senior leadership in the area and try to separate them from trying to rally" the Taliban's locally recruited soldiers, NATO spokesman Col. Tom Collins said.

One British soldier and four Taliban fighters were killed on Tuesday, the operation's opening day.

Separately, U.S.-led coalition troops detained five men suspected of involvement in anti-government activities and "known terrorist groups," in the eastern city of Khost, the coalition said without elaborating.

The troops uncovered a cache of grenades and armor-piercing rounds during their search, the statement said. No injuries occurred during the raid.

In southern Zabul province, Taliban militants attacked a police checkpoint and wounded four policemen Wednesday, said provincial police chief Abdul Ghafar. The militants fled after the attack, which occurred near Qalat, Zabul's capital.