HERAT, Afghanistan (Reuters) - Taliban insurgents have captured a third district in western Afghanistan, local officials said on Monday, defying Western assertions the rebels are unable to mount large military offensives.

Slideshow ( 6 images )

The hardline Islamist Taliban relaunched their insurgency two years ago to topple the pro-Western Afghan government and eject the 50,000 foreign troops, expanding their operations further from the mainly Pashtun south where they are strongest.

Western forces say the Taliban’s greater reliance this year on suicide and roadside bombs is a result of heavy battlefield casualties they and Afghan troops have inflicted on the rebels and the insurgents’ inability to hold ground.

But in the last week, the Taliban have captured three districts in the western province of Farah, bordering Iran, forcing lightly armed Afghan police to flee and defying Afghan and foreign forces to retake the lost ground.

First, Taliban rebels captured the Farah district of Gulistan a week ago, then on Wednesday took nearby Bakwa. On Sunday, the insurgents seized Khak-e Sefid without a fight.

“Khake-e Sefid district fell into Taliban hands yesterday without any resistance from Afghan forces,” Qadir Daqiq, a Farah provincial council member told Reuters. A provincial official who declined to be named also confirmed the report.

Taliban forces had been building up around Khak-e Sefid for some days, a Western security analyst said. The rebels in Farah have been receiving arms through a Taliban leader based close to the Iranian border, he said on condition of anonymity.

“There are many Iranians and Pakistanis fighting among the Afghan Taliban,” Farah provincial police chief Abdulrahman Sarjang told Reuters.

POLICE MORALE LOW

Afghan and Western officials have often said the Taliban’s ranks are reinforced with foreign fighters, but have said they have no proof of any assistance at an official level.

Poor morale among Afghan police meant that up to 38 officers had defected to the Taliban in the last week in Farah, the security analyst said, and those that remained were unwilling or unable to put up much of a fight.

“As soon as the Taliban attacked in numbers they did their best to make a tactical withdrawal -- they basically got out of there as quick as they could,” he said. “Their motivation is not there to fight.”

Local residents have complained that NATO-led troops, under Italian command in western Afghanistan, have not helped Afghan forces to retake the districts.

“The residents are complaining that foreign forces do not assist Afghan troops to retake the districts,” Maolavi Yahya, district chief of neighboring Delaram told Reuters. “They have been complaining for a week now.”

As fighting in Afghanistan drags on, frustration is growing among ordinary Afghans that their government and its Western backers have not provided security six years after Afghan and U.S.-led forces toppled the Taliban in 2001 for not handing over al Qaeda leaders in the wake of the September 11 attacks.

NATO commanders admit they have a limited window in which to defeat the Taliban and provide much-needed development before the Afghan public turns against their presence and public opinion in the West, frustrated by growing casualties, calls for the troops to be withdrawn, handing victory to the insurgents.