KABUL - Fighting in southern Afghanistan killed six Afghan police Sunday and a roadside bomb killed an Afghan soldier in the same region, the government said.

The clash in Helmand province started when insurgents attacked a police checkpoint in Nahri Saraj district in the early morning, the Interior Ministry said in a statement. Police arrested one of the attackers and sent search teams out to chase others, it said.

Meanwhile, a roadside bomb in Zabul province killed one Afghan army soldier and wounded three others, the Defence Ministry said.

U.S. President Barack Obama has ordered another 21,000 American troops to Afghanistan -- many of them to the south -- to try to turn back a growing Taliban insurgency. The militant group has been launching regular attacks on Afghan government and international forces and installations, and has promised more violence as more troops arrive.

In nearby Uruzgan province on Saturday, Afghan and international forces killed six insurgents in Dihrawud district, the Interior Ministry said.

Some of the first units sent as part of the summer surge started taking control of parts of operations in southern Afghanistan last week when the 82nd Combat Aviation Brigade of the 82nd Airborne Division assumed control of aviation operations at Kandahar airfield.

The new troops will bolster the record 38,000 American forces already in the country.