Hundreds of US and coalition forces are scouring caves in southern Afghanistan for rebel survivors after fierce fighting on Tuesday.

Enemy casualties are being assessed as the forces sweep this mountainous area Colonel Roger King US military

Up to 18 anti-government fighters were killed in what US military officials called the largest-scale fighting for nine months.

American war planes were called in to bomb the mountainous region near the town of Spin Boldak, close to the Pakistan border.

A US military spokesman said there had been no clashes since late on Tuesday.

Col King; Thorough search under way

"At least 160 caves have been counted so far," Colonel Roger King told reporters.

He said 200-400 US troops were involved in combing the cave complex, 100 kilometres (62 miles) east of the city of Kandahar, and that enemy casualties were still being assessed.

A number of men have been detained and weapons destroyed.

US and Afghan officials say they believe the fighters are aligned to the warlord Gulbuddin Hekmatyar, a former prime minister who has vowed to fight US forces on Afghan territory.

Gun battle

Tuesday's fighting was centred on rocky, unpopulated terrain around the Adi Ghar mountain, near the border with Pakistan.

The fighting was triggered by a small gun battle nearby between US Special Forces and armed attackers as the Americans and Afghan Government troops were working to clear a compound.

The allied forces surrounded the group - which locals said had been threatening communities east of Spin Boldak - killing at least one man and wounding another.

Apache helicopters sent to investigate came under fire, prompting the deployment of American B-1 bombers, F-16s and AC-130 gunships.

Recent attacks

Colonel King said that intelligence suggested the rebel fighters were most closely aligned with faction leader Gulbuddin Hekmatyar.

"The man who was detained talked about a link to Hezb-e-Islami, which is Hekmatyar's military group," he said.

The US miltary also say they have reports that the warlord has been attempting to consolidate with remnants of al-Qaeda and Afghanistan's former Taleban rulers.

However, the BBC's Rahimullah Yusufzai, reporting across the border from Peshawar, says there is little evidence that Mr Hekmatyar has joined forces with the Taleban.

Many Taleban and al-Qaeda suspects fled into Pakistan following the US bombardment in 2001.

Recent months have seen a series of attacks along the long border between the two countries.

Up to 8,000 US troops are in Afghanistan leading a coalition of forces hunting remnants of the Taleban and al-Qaeda, which the US blames for the 11 September, 2001 attacks on New York and Washington.