Afghan security forces block the road where Taliban suicide bombers attacked a joint U.S.- Afghan air base in Jalalabad, east of Kabul, Afghanistan on Sunday. (Nasrullah Khan/AP)

A squad of nine suicide bombers attacked a major U.S.-Afghan air base in the eastern city of Jalalabad just after dawn Sunday, detonating explosives at the front gate and sparking a lengthy firefight with Afghan and NATO forces inside.

Officials said all nine attackers died in the assault, which killed three members of Afghanistan’s security forces and two Afghan medical students. An American spokesman for the International Security Assistance Force, or ISAF, said three foreign troops were wounded.

The Taliban asserted responsibility for the attack, which was reminiscent of a frontal assault on the base in February, when a suicide attack left nine Afghans dead. The base, located at a former commercial and military airfield, is a major transport center for the U.S. military in eastern Afghanistan.

A Taliban spokesman, Zabiullah Mujahid, said in a message that “a number of our devotees” attacked the base and “brought heavy casualties to the enemy.”

A second spokesman, Abdul Balkhi, sent out tweets Sunday that described the attack in detail, some of which conflicted with accounts provided by the NATO coalition. Balkhi said two groups of Taliban fighters staged the assault, including six who were wearing U.S. military uniforms and who drove onto the base in a vehicle that they then detonated.

Balkhi said a second group fired at foreign troops in a two-hour gun battle before being “rewarded with martyrdom.” He said that two “enemy aircraft” had been destroyed and that much of the base had been “engulfed in flames.”

This triumphant account of the attack was partially contradicted by competing tweets and e-mails from ISAF spokesmen, who portrayed the assault as far less successful.

Lt. Col. Hagen Messer confirmed that the airfield was attacked at 6 a.m, but he stated that “no insurgents breached the ­perimeter.” Messer also said that U.S. helicopters were deployed to defend the base, which ISAF officials said was secured soon after the firefight ended.

A communique from the provincial governor’s office in Jalalabad, the capital of Nangahar province, said suicide bombers in two vehicles staged an attack at the front gate of the base, followed by three insurgents who tried to detonate their explosives but were fatally shot by ISAF and Afghan forces.

A spokesman for the provincial police chief said two trucks full of explosives rammed the front gate of the base, with one exploding. He said that Afghan guards started firing on the second truck and that it also exploded.

The bold assault was the third high-profile suicide attack by the Taliban in the past month. It followed one in a high-security area of Kabul that killed two Afghans and a more powerful blast in the capital of Wardak province, about 20 miles south of Kabul, that killed 3 Afghans and wounded more than 100.

Although Taliban attacks have decreased as winter weather sets in across the mountainous country, police and other officials said these carefully planned shows of strength were meant to weaken government resolve as the departure of NATO troops looms and bilateral talks with the United States on its long-term military role in Afghanistan get underway.

Javed Hamdard contributed to this report.