The detentions follow the discovery of suicide bomb vests, hand grenades, pistols and explosives in a hospital storeroom in Lashkar Gah, the capital of the southern province of Helmand, a spokesman for the provincial government said.

Police were tipped off about a plot to kill Helmand's governor during a future visit to the hospital, spokesman Daud Ahmadi said.

A video of the raid obtained by Associated Press Television News shows British troops accompanying Afghan police, soldiers and government officials to the city's Emergency Surgery Center for Civilian War Victims, run by the Italian private group Emergency.

In a storeroom, boxes are opened containing what appear to be bullets, pistols, hand grenades, and bags of explosives. A British soldier is heard saying that an explosives disposal unit was on its way.

Three foreign staff members are then shown sitting on outdoor benches, their identification cards visible but names unclear.

Helmand's governor, Gulab Mangul, confirmed the arrests at a news conference, saying those held included three Italians and six Afghans.