KABUL, March 8 (Reuters) - Taliban and NATO troops fought battles in southern Afghanistan on Thursday as the alliance pressed ahead with its biggest offensive to quash the insurgents.

With more than 4,500 NATO troops and 1,000 Afghan soldiers deployed, Taliban fighters sheltered in houses, NATO said. This could not be independently verified and the Taliban could not immediately be contacted for comment.

"This is not the first time Taliban extremists have used civilians as human shields," Lieutenant Colonel Stephane Grenier, spokesman for NATO's southern command, said in a statement.

NATO said a soldier died in the south on Thursday from combat injuries, but gave no further details.

Operation Achilles, which NATO says is its biggest in Afghanistan, was launched on Tuesday to head off a threatened spring offensive by the Taliban after last year saw the worst fighting since the Islamists were ousted in 2001.

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