Taliban fighters attacked a foreign military base at the main airport in eastern Afghanistan on Saturday, one of four incidents in 24 hours that marked a sudden upswing in violence.
Militants mounted attacks in Jalalabad and Kunar in the east and in Kunduz in the north, after an attack in the capital Kabul on Friday, apparently demonstrating their continuing strength despite NATO-led forces stating that they have made gains.
The attacks will send a message to NATO leaders meeting in Lisbon next week that the Taliban remain a formidable enemy. European NATO leaders are under particular pressure because popular support for the drawn-out war is sagging.
Saturday is the ninth anniversary of the Taliban's overthrow in Kabul by U.S-backed Afghan forces, a war waged because the Taliban harbored al Qaeda before the September 11, 2001, attacks on the United States and refused to hand over their leaders.
U.S. President Barack Obama is due to review his Afghanistan war strategy next month.
His commanders have been talking up recent successes and he remains committed to starting a gradual troop drawdown in July 2011, but increased violence would add to the Democrats' worries after their mauling in mid-term elections last week.
The attacks follow a growing acceptance among NATO allies of the need for a negotiated settlement, though peace talks are being approached gingerly.
The Taliban have in the past timed attacks to coincide with important events elsewhere in the world, and a sudden jump in such attacks now would not be surprising, analysts said.
The Taliban may at the same time be looking to position themselves again as a legitimate ruling group after defying the West's military strategy for nine years.
"From one side, the Taliban would like to show that the United States could not defeat them militarily in the past nine years and from other side want to introduce themselves as an acceptable political force, too," said Ghulam Jelani Zwak, director of the Afghan Analytical and Advisory Center.
Violence is at its worst across Afghanistan since the Taliban were overthrown in 2001, and civilian and military casualties are at record levels despite the presence of 150,000 foreign troops.
In Jalalabad, near Pakistan, at least eight insurgents, including two suicide bombers, attacked a forward operating base run by the NATO-led International Security Assistance Force (ISAF) which shares the main airport.
Smoke rose from the area and explosions and gunfire were heard, a Reuters witness said. Helicopters flew overhead and the bodies of at least one suicide bomber and one other attacker were seen near the airport.
"We killed six insurgents, two with suicide vests," an ISAF spokesman said. Afghan and ISAF troops responded to small-arms fire, the coalition said, adding that no Afghan or ISAF troops were killed.
A Reuters witness said the bodies of three fighters, dressed in Afghan army uniforms and carrying rocket-propelled grenades, small arms and a heavy machinegun, were lying near the base.
Taliban spokesman Zabihullah Mujahid said by telephone from an undisclosed location that 14 suicide bombers were involved in the attacks and that as many as 30 foreign soldiers had been killed. The Taliban often exaggerate the details of attacks and play down the number of their own casualties.
On October 30, the Taliban attacked a small outpost in nearby Paktika province. ISAF said at least 40 insurgents were killed while Afghan officials put the toll as high as 80.
Just north of Nangarhar province, of which Jalalabad is the capital, Taliban insurgents fought Afghan and ISAF troops in Kunar province for several hours. Three Taliban fighters were killed, ISAF said.
In Kunduz, a jumping-off point for attacks in the north over the past year, a bomb hidden on a motorcycle killed at least 10 civilians, including three children, and wounded 18, a district official and the Interior Ministry said.
Three ISAF service members died after an insurgent attack on Saturday in southern Afghanistan, ISAF said in a statement. It gave no details.
On Friday, a suicide car bomber hit a convoy of Afghan and ISAF troops on Kabul's outskirts, the first attack in the capital in three months, wounding two soldiers.