NATO-led troops launched an offensive against Taliban militants Tuesday in a volatile southern Afghan province where hundreds of militant fighters have amassed, as reports of a Briton and two Afghans being kidnapped surfaced.

The operation, which will eventually involve 4,500 NATO troops and 1,000 Afghan soldiers, was launched at the request of the Afghan government and will focus on the northern region of Helmand province, NATO's International Security Assistance Force said.

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"Our first maneuver elements reached their positions at approximately 5 a.m. this morning," said Maj. Gen. Ton van Loon, ISAF's southern commander.

Britain was looking into reports Tuesday that a British man has been kidnapped in the volatile south of Afghanistan, officials said, as the Taliban claimed to have captured a Briton and two Afghans.

A Taliban spokesman claimed the hard-line militia had detained the Briton — whom he did not name — and two Afghans as they traveled together by vehicle Monday in Nad Ali district of Helmand province.

"Taliban higher authorities" will decide what to do with them, Qari Yousef Ahmadi, who claims to speak for the Taliban told The Associated Press by satellite phone from an undisclosed location. "We are investigating whether they are British spies."

British Prime Minister Tony Blair's official spokesman, speaking on condition of anonymity according to government policy, said the Foreign Office is investigating the claims. He said it was too early to be sure whether reports that a British freelance reporter and two Afghans had been kidnapped were correct.

Dubbed Operation Achilles, the offensive is NATO's largest-ever in the country. But it will involve only half the number of soldiers who fought in a U.S. offensive in the same region just nine months ago, when some 11,000 U.S.-led troops attacked fighters in northern Helmand province during Operation Mountain Thrust.

NATO said that Achilles initially would focus on improving security conditions, but that its "overarching purpose is to assist the Islamic Republic of Afghanistan (to) improve its ability to begin reconstruction and economic development."

The government has little control over many parts of northern Helmand, and the British troops stationed there fight almost-daily battles with militants. U.S. intelligence officials say Taliban fighters have flooded into Helmand the last several months, and that there are now more fighters there than any other part of the country.

The militants overran Musa Qala, in central Helmand province, on Feb. 1 after defying a peace deal between the government and elders reached last fall that capped weeks of fighting. The Taliban still control the town more than a month after the initial attack.

British troops also have been battling militants in the nearby district of Kajaki, in northern Helmand, to enable repair work on a hydro-electric dam there, which supplies close to 2 million Afghans with electricity.

"Strategically, our goal is to enable the Afghan government to begin the Kajaki project," van Loon, said.

"This long-term initiative is a huge undertaking and the eventual rehabilitation of the Kajaki multipurpose dam and power house will improve the water supply for local communities, rehabilitate irrigation systems for farmlands and provide sufficient electrical power for residents, industries and commerce," he said.

Helmand is the world's biggest producer of opium, and a new U.N. drug assessment indicates that the this year's poppy harvest will be higher than last year's record output. The U.N. says Taliban fighters protect poppy farmers and tax the crop, deriving much-needed income for their insurgency.

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