About 7,000 US and Afghan government forces launched an offensive against the Taliban in central and eastern Afghan provinces yesterday, as a blast near Kabul killed three Afghan aid workers.

Operation Mountain Fury is the third offensive launched in recent weeks against a resurgent Taliban who have unleased the worst phase of Afghan violence since they were ousted in 2001.

"Mountain Fury is just one part of a series of co-ordinated operations placing continuous pressure on Taliban extremists across multiple regions of the country," the US military said in a statement.

About 10,000 NATO and Afghan troops have in recent weeks mounted a big offensive in the southern province of Kandahar, killing hundreds of militants in the Taliban heartland. Troops from a separate US-led force have been battling insurgents in the eastern province of Kunar, on the Pakistani border, in a third offensive.

Operation Mountain Fury was aimed at defeating the Taliban in the provinces of Paktika, Khost, and Paktiya, all in the east on the Pakistani border, as well as in neighbouring Ghazni and Logar provinces, the US military said. The offensive involved 3,000 US-led troops and 4,000 Afghans.

Later yesterday, the US military said a US coalition soldier training Afghan troops was killed in an attack on a base near the Pakistani border. Another coalition soldier and an unspecified number of Afghan soldiers were wounded.

The level of violence this year has surprised the government and its Western allies and raised concern about the prospects for a country that had been seen as a success in the war on terrorism.

While international and Afghan troops have been launching offensives in the south and east, militant attacks have also increased in parts of the country previously considered safe, including Kabul and the west.

Earlier yesterday, a blast hit a car on a road just to the south of Kabul, killing three Afghan aid workers and wounding one, police said. Kabul police official Alishah Paktiawal said he did not know which aid group they were from.

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