KUNDUZ, Afghanistan >> This city, once a crossroads in the country’s northeast, is increasingly besieged. The airport closed months ago to commercial flights. The roads heading south to Kabul and east to Tajikistan as well as north and west are no longer safe for Afghans, let alone Westerners.

Although the numbers of U.S. and German troops in the north have more than doubled since last year, insecurity has spread, the Taliban are expanding their reach and armed groups that purportedly support the government are terrorizing local people and hampering aid organizations, according to international aid workers, Afghan government officials, local residents and diplomats.

The growing fragility of the north highlights the limitations of the U.S. effort here, hampered by waning political support at home and a fixed number of troops. The Pentagon’s year-end review will emphasize hard-won progress in the south, the heartland of the insurgency, where the military has concentrated most troops. But those advances have come at the expense of security in the north and east, with some questioning the wisdom of the focus on the south and whether the coalition can control the entire country.

“The situation in the north has become much more difficult, a much stronger insurgency than we had before,” said a senior Western diplomat, who asked not to be named because of the sensitivity of the subject. “We have to get these better under control.”

The NATO command has largely defined Afghanistan’s instability in terms of the Taliban insurgency, which is the most recent fight here but hardly the only one that looms in people’s memories. For many, the period 20 years ago when mujahedeen warlords divided the country into fiefs shapes their current fears. It was the behavior of the warlords, among other factors, that drove people into the arms of the Taliban in the 1990s.

“The north has its own logic,” said Pablo Percelsi, the director of operations in northern Afghanistan for the International Committee of the Red Cross, which has had a staff and presence here for 30 years. “The Taliban are only a small part of the equation.

”You have the whole fabric of the militias,“ he added. ”There are groups that collect money, and they collect it from civilians and by doing kidnapping and bold actions against internationals.“

NATO’s current strategy aims to transform many of these militias into local police forces that would augment the often thin national police. However, many local Afghan officials worry that the plan legitimizes the groups, some of whom are little more than thugs, and amounts to putting government uniforms on gunmen whose real loyalty is to their local strongman.

Sometimes known as ”arbekais,“ these armed groups include semi-official militias organized and paid by the Afghan intelligence service; others are simply armed gangs who prowl through villages demanding food, shelter or money. Some are headed by former mujahedeen, strongmen who fought the Soviets; some are cobbled together by village elders. Still others, particularly in Takhar province, are little more than protection for warlords who traffic narcotics along a drug transport corridor that runs to the Tajik border, according to military intelligence officials.

”There’s a major narco-drug corridor, and the militias are protecting that,“ said a NATO intelligence official who spoke on condition of anonymity because he is not permitted to speak to reporters.

The abuses of the armed groups, along with the growing disenfranchisement of Pashtuns who won few seats in Parliament in most northern provinces, has begun to make the Taliban more attractive for those who are already disillusioned with the government.

“It is the carelessness of the government that the Taliban have come back,” said Mahboobullah Mahboob, the chairman of the Kunduz Provincial Council, who is a Tajik. “They returned here and they started to grow, and the government didn’t pay attention. We implored the central government repeatedly because the local government couldn’t counter them.”

Hajji Aman Uthmanzai, a Pashtun colleague on the provincial council, agreed but added that the Taliban also offered speedy justice, and the government did not. The government has not protected people either from the Taliban or the militias, so villagers feel caught between the two.

“The government claims they established arbekais to protect the villages, but if you go to the villagers and ask the villagers some will even say they prefer the Taliban, because the arbekais are harassing them, taxing them,” he said.

The Taliban have begun to spread throughout the north to areas that were previously untroubled, like the provincial capital of Sar-i-Pul and the neighboring province of Faryab. More than 50 Taliban fighters — some officials put the number at 150 — staged a complex attack in Sar-i-Pul on Oct. 24 to try to win the release of Taliban prisoners.

In the northwest corner of the province, foreign extremists have made themselves a haven, according to NATO intelligence officials as well as the governor of Sar-i-Pul, Sayed Anwar Rahmati.

The proliferation of armed groups has left organizations, including the Red Cross, struggling to keep projects afloat. Since they work without armed security, they have to persuade local strongmen to allow their staffs to operate unimpeded. Doctors Without Borders is weighing whether to open a clinic but found the number of armed groups there daunting, said Michiel Hofman, the country representative.

It used to be that such negotiations were time consuming but possible. Now humanitarian officials say there are so many armed groups that it is difficult to get guarantees from all of them.

”Every five kilometers there’s a different commander with no central command structure,“ Hofman said.

The insurgency here includes extremists from Tajikistan and Uzbekistan, although much of the rank and file is Pashtun, according to U.S. intelligence and military officials. In the past two months, NATO officials announced the killing and capture of several Uzbek militants.

An estimated 25 Tajik extremists took up residence in an inaccessible border area of northern Kunduz province, according to a NATO intelligence officer as well as the Kunduz police chief, Abdul Rahman Sayid Khali.

In the meantime the armed groups continue to maraud in the northern provinces.

”We are trying to bring them into the police,“ Rahman said. ”We’ll give them police uniforms and bring them under police discipline.“

Might they end up extorting people while in uniform? Rahman, a former Northern Alliance mujahedeen commander himself, shrugged and picked his teeth with the business card of the reporter interviewing him.

“Their salaries will be lower than that of normal police,” he admitted, but he said it was hard to tell if that would make a difference. “We don’t know how much they are making now.”

At dawn on the edges of Kunduz city, taxi drivers herd passengers into scuffed Toyota corollas and KIA minibuses for the dangerous drive north to Imam Sahib district or west to Chardara, eager to make the most of the safer daylight hours. Once dusk falls, they are at risk from both the Taliban and armed militias.

“After 6 p.m. the road is absolutely dangerous,” said Ismatullah, 35, a taxi driver from Imam Sahib district. “Many times my car has been looted by unknown armed people. Who knows — are they arbekais, Taliban or are they our own police?”

© 2010 The New York Times Company