KABUL, Afghanistan (CNN) -- Afghan troops, backed by Canadian forces, launched an operation Wednesday to push Taliban militants from villages in southern Afghanistan as the UK revealed four more of its troops had been killed.

Canadian soldiers are backing Afghan troops as they try to oust the Taliban from villages in southern Afghanistan.

The operation is targeting villages in the Arghandab district of Kandahar province, where 400 militants escaped from prison in a jailbreak Friday.

The four British soldiers were killed Tuesday in a separate operation in Lashkar Gah, also in southern Afghanistan.

The troops began moving into Arghandab Wednesday morning, said Afghan Defense Ministry spokesman Gen. Zahir Azimi.

By noon, the soldiers had gotten into "minor clashes" with insurgents, but no casualties had been reported, said Mark Laity, a spokesman for the NATO-led International Security Assistance Force (ISAF).

Even with the operation underway, NATO said it had seen no evidence of an increased Taliban presence in the region.

"The scale of the challenge is currently unknown but what we failed to find is the large grouping [of militants] that some people claimed," Laity said.

He said the reports of militants overrunning villages was Taliban "propaganda" meant to scare people.

The Afghan army and police were conducting the operation with assistance from Canadian troops, who are part of the NATO alliance.

Throughout the night and into early Wednesday morning, residents saw row upon row of military convoys moving into the district. As the operation got underway Wednesday morning, planes and helicopters buzzed overhead, residents said.

Local elders said hundreds of militants streamed into the villages late Sunday night on motor bikes and pickups. Then, in apparent preparation for an impending military operation, they planted mines, destroyed bridges and forced villagers to stay and fight alongside them, a tribal elder said.

NATO aircraft dropped hundreds of leaflets Monday asking residents to stay inside their homes, saying troops were "coming to remove the enemies of Afghanistan."

Even as they did so, however, NATO and U.S. authorities said they had seen no evidence of an increased Taliban presence in the region.

"Today ISAF soldiers along with the ANSF [Afghan National Security Forces] conducted a show of force in Kandahar City and Arghandab District," said Col. Jamie Cade, deputy commander of Task Force Kandahar, in a statement Wednesday. "There were no obvious signs of insurgent activity and it is clear that Kandahar City remains firmly under the control of the Afghan government and its people."

The ISAF statements contradicted comments by Afghan officials, who said they had deployed thousands of troops -- with reinforcements from the capital city of Kabul -- to rout the rebels.

Locals differed on the number of villages they said the Taliban had seized, with figures varying from five to 13.

The villages are about 20 km (12 miles) north of Kandahar, near the prison. Kandahar province is where the Taliban first rose to power and where it made its last stand before being toppled by U.S.-led forces in late 2001.

Meanwhile, the British soldiers were killed as they took part in an operation east of Lashkar Gah, the British Ministry of Defence said in a statement.

The blast killed three soldiers immediately while a fourth died later, the ministry said. One of the victims served in the Intelligence Corps.

A fifth soldier was wounded and is in stable condition.

Prime Minister Gordon Brown mourned the loss.

"They were in the most dangerous of jobs in the most difficult of circumstances. I salute not just their bravery, dedication and professionalism but that of all our armed forces," he said in a statement. "Our troops are the best in the world and fighting for the noblest of causes."

The explosion occurred a day after Brown announced that Britain would send more troops to Afghanistan. British troops there primarily serve in the southern province of Helmand, where allied forces are battling a resurgent Taliban.

Defense Secretary Des Browne said Britain would increase its troop presence in Afghanistan from 7,800 to 8,030 by next spring.

-- Journalist Farhad Peikar contributed to this report

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