KABUL, Feb 27 (Reuters) A blast near the gates of the main US base in Afghanistan, where US Vice President Dick Cheney is visiting, killed several people today, a witness said.

The cause of the explosion outside Bagram airbase, 60 km north of Kabul was not immediately known. Cheney stayed at the base overnight after planned talks with Afghan President Hamid Karzai were delayed by weather.

''The Vice President is fine,'' spokeswoman Lea Anne McBride said.

An official at the base confirmed the blast, but had no details.

Bagram is a sprawling complex and the main gates are some distance from offices and living quarters.

An Afghan official said the explosion occurred inside a shipping container, but gave no more details, the Pakistan-based Afghan Islamic Press.

Some containers are used as shops in the market lining the road to the base. Others are carried on trucks to bring supplies into the base.

A Reuters correspondent travelling with the US delegation said they were not aware of the blast until they heard sirens and were told by a military spokesman that the base was ''under attack''.

''We were told there was a 'red alert','' Caren Bohan said.

''There was a commotion, but it ended pretty quickly. We didn't hear any bomb or anything like that from where we were.'' REUTERS BDP RAI1217