NATO's most ambitious offensive against Taliban strongholds in Helmand province entered its second day on Sunday, with officials claiming 27 insurgents killed.
Thousands of US Marines, Afghan and British forces were inserted by dozens of helicopters and armoured vehicles into Marjah and Nad Ali districts in the southern province Saturday.
The military operation is the largest since the ouster of Taliban regime by a US-led invasion in late 2001.
NATO officials claimed early success as troops cleared 13 targeted locations in the two districts, strategically important bastions in the country's main opium-producing region.
"The operation is going on successfully," Daoud Ahmadi, spokesman for Helmand's provincial governor, said. He said seven insurgents were killed since Saturday night, bringing the total Taliban death toll to 27.
He said the combined forces also discovered and destroyed more than 2,500 kg of explosives.
Two NATO soldiers, one British soldier and a US marine were also killed in the first day of the operation, Ahmadi said. The British Defence Ministry also confirmed in a statement posted on its website that a soldier from 1st Battalion Grenadier Guards was killed by an explosion in Nad Ali district.
General Abdul Rahim Wardak, Afghan defence minister, said in Kabul Saturday that there had been some injuries among Afghan forces.
Wardak said several hundred Taliban fighters were still in the area, while a large number of the insurgents had fled before the start of the operation, which was announced weeks prior. Other NATO and Afghan officials estimated that from 600 to 1,000 Taliban were entrenched in the two targeted districts.
A total of 15,000 troops, including US, Afghan, British, Canadian, Danish and Estonian personnel were mobilised for the operation.
The operation, dubbed Mushtarak or "together", is centred on Marjah, inhabited by about 80,000 people, where Taliban-protect traffickers had set up the biggest drug market in the country.
Hundreds of local residents of Marjah and neighbouring Nad Ali have fled to provincial capital Lashkargah, but many others remained amid assurances by NATO officials that measures would be put in place to avoid civilian casualties.
Officials said roadside bombs had slowed the advance of combined forces moving through Marjah town.
Taliban spokesman Qari Mohammad Yousif Ahmadi, speaking by phone from an undisclosed location, said on Sunday that their fighters had not retreated.
The combined forces held meetings with groups of Afghan local elders in the area, a NATO military statement said Sunday. "More shuras (local councils) are anticipated in the coming days".
The offensive, a first test of new US strategy to turn the tide of the eight-year-war, aims to extend the Afghan government's authority in the Taliban-controlled areas and begin reconstruction to win the hearts and minds of civilians.
US President Barack Obama increased the US troop commitment by another 30,000 troops, bringing the US presence to 98,000 soldiers. The US and NATO together have around 113,000 troops currently in the country, and some NATO countries have pledged to send up to 7,000 more troops by this summer.