GARDEZ, Afghanistan ? U.S. warplanes and Afghan troops backed by U.S. Special Forces launched a major attack Saturday on Taliban and al-Qaida forces regrouping in the rugged mountains of eastern Afghanistan. Defenders fought back with mortars, rockets and heavy machine guns.

The offensive against Taliban and al-Qaida holdouts marked the largest air and ground operation in weeks, and signaled one of the most robust uses of helicopter gunships of the 5-month-old U.S. air campaign.

Pakistan closed its border to prevent escape by any al-Qaida or Taliban members fleeing the fight. Associated Press reporters saw U.S. military helicopters rushing Saturday toward the snowy mountains where the battle was waged.

U.S. military officials at Central Command headquarters in Tampa, Florida confirmed the offensive, but refused to give details, citing confidentiality of ongoing missions.

“We have surrounded the al-Qaida and Taliban,” declared Saif Ullah, a member of the local governing council in Paktia province’s Gardez, 40 kilometers (20 miles) north of the assault

It was unclear whether the U.S.-backed Afghans overran any Taliban or al-Qaida positions. Ground fighting ceased in the early afternoon, Afghan commanders said, but U.S. heavy aircraft could be heard flying overhead into the evening.

Up to 5,000 Arabs, Chechens, Pakistanis and other foreign fighters are believed still in Afghanistan – many of them, hiding in the Paktia province mountains, as well as in other provinces along the Pakistan border, according to U.S. officials and Afghan sources.

Remote, rugged and honeycombed with caves, the mountains around Gardez have been a hiding place for Afghan warriors since anti-Soviet guerrillas used them as a base for their fight against Soviet troops in the 1980s.

Former Taliban front-line commander Saif Rahman was believed to be leading the Taliban and Taliban-allied foreign forces still in hiding there.

Paktia was also a stronghold of Jalaluddin Haqqani, a U.S.-backed rebel commander in the 1980s who joined the Taliban and is sought by U.S. authorities.

Neither the former Taliban supreme leader Mullah Mohammed Omar nor al-Qaida chief Osama bin Laden are believed to be in the area.

American warplanes and helicopters opened the attack Friday night, pounding suspected al-Qaida and Taliban hide-outs into Saturday morning.

AP reporters saw a dozen U.S. military helicopters taking off from a landing strip in Logar province south of Kabul on Saturday, kicking up clouds of brown dust as they sped away. They included at least one transport helicopter. Local residents said the helicopters had been shuttling weapons and ammunition toward the area of fighting since dawn.

“The Americans said `first we are bombing, and then we will launch an attack,'” fighter Jan Mohammed said at Gardez, interviewed late Saturday at one of two compounds that American Special Forces have made their base.

“The helicopters were rocketing, and the planes were bombing. It was too much,” a doctor, Naguibullah, said at a Gardez hospital.

Americans and their Afghan allies threw at least 380 Afghan fighters, moving with about 30 American Special Forces, into the offensive Saturday. Afghan forces wore black wool caps with white pieces of paper on the tops, so U.S. helicopter pilots could distinguish them from Taliban and al-Qaida.

Al-Qaida and Taliban fighters defended the high ground with mortars, rockets and heavy machine guns, the Afghans said.

U.S.-allied Afghans suffered at least one death – a fighter hit in the face by shrapnel from an enemy mortar shell, Dr. Naguibullah said. No injuries were reported among the Americans.

“Our goal since the beginning … has been to eliminate al-Qaida and Taliban elements in the country, so they cannot reconstitute,” said Maj. A.C. Roper, spokesman for the U.S. Army’s 101st Airborne division at southern Afghanistan’s American-held Kandahar airport.

“We are moving methodically to identify those elements so we can achieve that goal,” Roper said.

Afghan officials say al-Qaida and Taliban fighters are regrouping in the mountains and just over the border in Pakistan, urging the faithful to wage holy war against U.S. forces.

Wives and children of al-Qaida, along with widows and families of al-Qaida dead, also are believed to be in hiding there.

The al-Qaida fighters are receiving support from a variety of groups, including Kashmiri separatists, Islamic militants in Pakistan and some former officials of Pakistan’s intelligence service, according to Afghan sources.

In Pakistan, a senior government official at the Pakistan border town of Miran Shah said Saturday that troops have blocked all routes to prevent escape of any al-Qaida and Taliban fleeing the attack.

The official, Javed Marwat, said a 110-kilometer (60-mile) strip with Afghanistan has been closed.

A tribal elder in the area, Haji Rasool Khan, said by telephone that his Madakhel tribe would not give shelter to any al-Qaida on the run.

The bombardment would be the United States’ largest-known attack since bombing in January against the al-Qaida cave complex at Zawar Kili in Paktia province.

America’s last reported ground operation in Afghanistan came Jan. 23, and failed – mistakenly killing at least 16 Afghans who turned out to be neither Taliban nor al-Qaida, the Pentagon acknowledged this month.

Smaller, undisclosed raids have taken place since, one U.S. defense official said, speaking on condition of anonymity. Those raids have concentrated on gathering information about pockets of resistance, and have at times netted documents, or individuals who were interrogated or then releasd, the official said.