KABUL — A team of gunmen and suicide bombers Saturday attacked the largest NATO base in a troubled province near the border with Pakistan, the latest in a string of insurgent assaults on major Western military installations in recent months.

The attackers were driven off, Western and Afghan officials said, and at least 20 of them were killed and five captured. The NATO force reported no casualties among its troops, but Afghanistan’s Interior Ministry said two of its soldiers were killed and three wounded.

The predawn onslaught, which lasted several hours, targeted Forward Operating Base Salerno, the main Western base in Khowst province in eastern Afghanistan, and a smaller adjacent installation known as Camp Chapman. In December, a suicide bomber killed seven people working with the CIA on staff or on contract at Camp Chapman.

In the last four months, Taliban fighters and other insurgents have carried out fruitless strikes against large, heavily fortified air bases at Kandahar, in the south; Jalalabad, in the east; and Bagram, north of Kabul, the capital.

The rash of coordinated attacks on major installations, a departure from the insurgents’ usual hit-and-run ambushes, appears to be intended to rattle Western troops with a symbolic show of zeal and a willingness to die.

Such frontal assaults by the Taliban and other insurgents were once rare because it would be very difficult for them to overrun well-armed bases of that size. Two of Saturday’s attackers did manage to penetrate the perimeter at Salerno, but were killed immediately, the North Atlantic Treaty Organization force said.

Khowst’s police chief, Abdul Hakim Hisaq Zai, said the insurgents were armed with rocket-propelled grenades, mortars and suicide vests. He said Afghan and Western forces seized a number of weapons and two vehicles packed with explosives.

The attack was thought to have been carried out by the Haqqani network, a Pakistan-based insurgent faction with deep roots in Khowst. Special operations troops for months have been carrying out raids aimed at Haqqani field commanders.

Also Saturday, the office of President Hamid Karzai denounced reports that senior Afghan government officials have been on the payroll of the CIA.

But the presidential palace did not specifically deny a report in The New York Times that Karzai aide Mohammed Zia Salehi, who is at the center of a major corruption scandal, was being paid by the CIA.