The operation was launched Friday after insurgents fired rockets on an Afghan National Army post in southeastern Zabul province's Day Chopan district, about 300km southeast of Kabul.

"The joint US and Afghan operation killed at least 12 Taliban including their top commander Sediqullah Sediqi," provincial deputy security commander Colonel Ghulam Jailani Farahi told AFP.

"The search operation is still ongoing to chase the remnants of Taliban fighters in the area," he said via satellite phone, adding that five militants had been arrested.

However, Taliban spokesman Abdul Latif Hakimi said that Sediqi had not been captured or killed by coalition forces.

Zabul, along with southern Kandahar province and central Uruzgan, is believed to be a Taliban stronghold. Regular attacks on coalition and Afghan troops, aid workers and reconstruction companies occur in all three provinces.

In a separate incident, three civilians were killed and two soldiers injured when suspected Taliban attacked Deh Rawood district in Uruzgan early Friday.

While early Saturday morning a suspected militant commander was arrested during a night patrol in Day Chopan.

"We arrested another Taliban commander, Mullah Taib, with an AK-47 on his motorbike in Jilda area of Day Chopan district," Farahi said.

Mullah Taib is believed to be leading a 15-member guerrilla group in the rugged mountains of Zabul.

The pace of violence has recently increased in south, southeast and eastern Afghanistan ahead of historic presidential and parliamentary elections scheduled for September.

Taliban have vowed to disrupt the elections. Bomb attacks targetting electoral workers in east of the country left two female voter registration workers dead last week.

On Friday a coalition convoy and, in a separate incident, a district governor escaped unhurt land mine attacks in southeastern Khost province near the border with Pakistan.

Some 20,000 US-led coalition troops, usually aided by Afghan national army or pro-government militiamen, are fighting Taliban remnants, al-Qaeda militants and other insurgents in Afghanistan, mainly in the south and south-east.