Taliban suicide attackers struck at a NATO base on an Afghan city airport at dawn on Sunday, killing five people and wounding several foreign troops in a two-hour battle, officials said.
NATO helicopters went into action, firing on the insurgents as they tried to storm the base after two suicide car bombs hit the perimeter gate of the Jalalabad airport near the Pakistan border.
A total of eight attackers armed with rocket propelled grenades and automatic weapons were killed, Afghan officials said.
The assault came as the usual summer fighting season should be drawing to a close, indicating that the insurgency remains resilient after surviving the biggest onslaught US-led forces will throw against them.
The last of the extra 33,000 soldiers President Barack Obama deployed in a "surge" nearly three years ago left in September, and the vast majority of the remaining NATO force of more than 100,000 will follow by the end of 2014.
One of the aims of the surge was to put so much pressure on the Taliban that they would come to the negotiating table, but the insurgents called off early contacts in March.
The hardline Islamists have waged an 11-year insurgency against the Afghan government since being overthrown in a US-led invasion for harbouring Al-Qaeda leader Osama bin Laden.
The Taliban claimed its militants had managed to enter the base and caused heavy casualties but this was denied by NATO's International Security Assistance Force (ISAF).
"Insurgents including suicide bombers attacked the perimeter of the Jalalabad air base this morning," a spokesman told AFP. "None of the attackers succeeded breaching the perimeter.
"I can confirm that there were helicopters involved in the coalition response to the attack.
"A number of ISAF forces were wounded," he added, noting that it was ISAF policy not to disclose the toll of those injured.
The airport complex has multiple layers of security, with the NATO base set well back from the first entrance, which an Afghan official said had been breached.
Three Afghan guards were killed and 14 wounded, while two civilians also died and four others were injured, police spokesman Hazrat Hussain Mashriqiwal told AFP.
"First there was a car bombing next to the entrance followed by gun attack by the insurgents," a senior Afghan security official said. "They couldn't reach NATO forces and they were killed in the area between the first and second gates."
The Taliban claimed their militants had entered the airport and caused heavy casualties.
"First a fedayee (suicide bomber) mujahid... detonated a car bomb causing the enemy heavy casualties and losses and removed all the barriers," the Taliban said on their website.
"After the attack other fedayee mujahids entered the base... and started attacking the invading forces in the base."
The interior ministry said in a statement that "suicide attacks are an indication of weakness of the Taliban terrorists.
"These enemies of peace and stability must understand that such cowardly, un-Islamic and inhuman attacks can not deter Afghan security forces from serving the suffering Afghan nation."
The Jalalabad airport has come under attack on two previous occasions this year.
But the biggest attack on a coalition base this year came in September, when insurgents stormed Camp Bastion in the south, destroying six fighter aircraft in the largest single loss of air assets for the United States since the Vietnam War.