Italy said yesterday it was unhappy with the way Afghan authorities were handling the arrest of three Italian aid workers accused of plotting an assassination, and asked to know the evidence against them.

An Italian doctor, nurse and logistics officer who work for the Milan-based charity Emergency were arrested on Saturday in the southerly Helmand province and accused of plotting to kill the province's governor.

"I am not satisfied with the response of the Afghan authorities," Italian Foreign Minister Franco Frattini told a parliamentary hearing.

He said the suspects had not yet had access to a lawyer.

"We want to know the evidence and see their defence rights fully respected," he said, adding that Prime Minister Silvio Berlusconi had written to President Hamid Karzai about the case.

The aid workers were taken from a hospital run by Emergency in Lashkar Gah, the capital of Helmand. The province is Afghanistan's most violent, and the scene of a massive assault by US and British forces against Taliban insurgents.

Provincial authorities said six Afghans had also been arrested, and that explosive suicide vests, hand grenades and pistols had been found at the charity's hospital.

Emergency has denied the accusations, accusing the Kabul government of targeting it to get rid of a "troublesome witness" to the suffering of civilians caught up in the fighting.