KABUL, Afghanistan - Taliban insurgents mounted their most serious attacks in six years of fighting in Afghanistan over the past two days, including a coordinated assault by at least 10 suicide bombers against one of the largest American military bases in the country, and another by some 100 insurgents that killed 10 elite French paratroopers.
The attack on the French, which took place in a district near Kabul, added to the sense of siege around the capital and was the deadliest single loss for foreign troops in a ground battle since the U.S.-led invasion chased the Taliban from power in 2001.
Taken together, the attacks were part of a sharp escalation in fighting as insurgents have seized an opportunity to press their campaign this summer - taking advantage of a wavering NATO commitment, an outgoing American administration, a flailing Afghan government and a Pakistani government in deep disarray that has given the militants freer rein across the border.
As a result, this year is on pace to be the deadliest in the Afghan war so far, as the insurgent attacks show rising zeal and sophistication. The insurgents are employing not only a growing number of suicide and roadside bombs, but are also waging increasingly well-organized and complex operations using multiple attackers with different types of weapons, NATO officials say.
NATO and American military officials blame much of the increased insurgent activity on the greater freedom of movement the militants have in Pakistan's tribal areas on the Afghan border.
The turmoil in the Pakistani government, with the resignation of President Pervez Musharraf on Monday, has added to the sense of a vacuum of authority there.
But at least as important, the officials say, is that Pakistan's military has agreed to a series of peace deals with the militants under which it stopped large-scale operations in the tribal areas in February, allowing the insurgents greater freedom to train, recruit and launch attacks into Afghanistan.
More foreign fighters are entering Afghanistan this summer than in previous years, NATO officials say, an indication that al-Qaida and allied groups have been able to gather more foreigners in their tribal redoubts.
The push by the insurgents has taken a rising toll. Before the attack on Monday, 173 foreign soldiers had been killed in Afghanistan this year, including 99 Americans. In all of 2007, 232 foreign troops were killed, the highest number since the war began in 2001.
The attack with multiple suicide bombers, which struck Camp Salerno in the eastern province of Khost, wounded three American soldiers and six members of the Afghan Special Forces, according to Afghan officials.
It was one of the most complex attacks yet in Afghanistan, and included a backup fighting force that tried to breach defenses to the airport at the base.
The assault followed a suicide car bombing at the outer entrance to the same base on Monday morning, which killed 12 Afghan workers lining up to enter the base, and another attempted bombing that was thwarted later.
A Taliban spokesman, Zabiullah Mujahed, reached by telephone at an unknown location, said on Monday evening that the attack was carried out by 15 suicide bombers, each equipped with machine guns and explosive vests, and backed up by 30 more militants.
He also claimed that some of the bombers had breached the walls of the base and had killed a number of American soldiers and destroyed equipment and helicopters.
This last claim was denied by Gen. Zaher Azimi of the Afghan military.
France's top military official, Gen. Jean-Louis Georgelin, said that most of the French casualties came in the minutes after the soldiers ascended a mountain pass.
Battles ensued, and 21 French soldiers were wounded.
French Defense Minister Herve Morin said about 30 militants were killed and 30 wounded, while Afghan officials said that at least 13 militants were killed.
Attacks involving large numbers of militants mark a tactical departure for the insurgents, who have generally eschewed large-scale frontal assaults in favor of smaller hit-and-run attacks that allow them to melt away when NATO troops use their superior firepower.
The Los Angeles Times and the Associated Press contributed to this article.