A roadside bombing in southern Afghanistan resulted in three Canadian soldiers dead, officials said on Friday.

The soldiers, who were serving under the NATO-led International Security Assistance Force (ISAF), were in a vehicle when it was struck Wednesday by the bomb in the Zherai district of Kandahar province, the Canadian military said.

"All four soldiers were evacuated to Kandahar Airfield," Brigadier General Denis Thompson, a Canadian military commander, told reporters at the base. "Sadly, three of the soldiers were confirmed dead by medical authorities."

The injured soldier was reported to be in serious but stable condition, he said.

The ISAF in Kabul also confirmed the deaths of its soldiers in a statement issued Friday.

Three Polish soldiers in the ISAF were killed in a similar roadside attack Wednesday in the east-central province of Ghazni while a day earlier, 10 French soldiers were killed in a Taliban ambush east of Kabul.

Taliban militants have stepped up their attacks against Afghan and international forces in the past three months, using mostly suicide and roadside bombings.

More than 180 international soldiers and more than 3,000 other people - mostly insurgents - have been killed in Afghanistan so far this year.