A U.S. army flight medic delivers a stretcher that will be used to carry a U.S. marine wounded in a rocket-propelled grenade attack in Marjah on Saturday. The smoke is from a grenade used to mark the landing spot. (Brennan Linsley/Associated Press)

Thousands of coalition soldiers are advancing Saturday into the Taliban stronghold of Marjah in Afghanistan's southern Helmand province.

Mines and booby traps were the main problems the troops encountered. Two coalition soldiers and 20 Taliban fighters had been killed, coalition spokesmen said.

U.S. Marines and Afghan soldiers led the attack on Marjah, while seven Canadian helicopters delivered 1,100 British and Afghan soldiers in the Nad Ali region north of Marjah. It was the biggest air assault that Canada has ever done, Canadian helicopter commander Lt.-Col. Jeff Smyth said.

Three Canadian Chinook helicopters, escorted by four Canadian Griffons, delivered the soldiers safely, said Col. Christian Drouin, commanding officer of the Canadian air force in Afghanistan.

"We had no resistance whatsoever."

The Marjah operation was also going "without a hitch," said Maj.-Gen. Nick Carter, NATO commander of forces in southern Afghanistan.

However, Taliban spokesman Qari Yousef Ahmadi told The Associated Press by phone that, "all of Marjah is still under Taliban control."

And despite the coalition confidence, the British Ministry of Defence said one soldier was killed in an explosion north of Marjah. A NATO soldier from an undisclosed country was shot dead, a coalition spokesman said.

A handful of Canadian troops are involved in Operation Moshtarak, which means "together" in Dari. The 34 soldiers are mentoring Afghan troops.

The attack, involving about 15,000 coalition soldiers, is intended to drive an estimated 1,000 Taliban out of the main locations they hold in Helmand province. It's part of a new NATO strategy designed to win Afghans over by protecting civilians.

Once the coalition controls Marjah, a city of 80,000, the plan is to deliver aid and restore public services.

International development workers and Afghan officials will enter the city as soon as it is secure. Government teams have plans for new schools, clinics and mosques.

In an incident unrelated to Operation Moshtarak, three U.S. soldiers were killed by a bomb, NATO said.

With files from The Canadian Press and The Associated Press