One Portuguese soldier was killed and three others were injured in Afghanistan when their vehicle exploded while they were on patrol in Kabul today, the defence ministry said.

A second vehicle with Portuguese soldiers, which was part of the same patrol, was not harmed.

There were just four soldiers onboard the vehicle when the blast took place early this morning. The cause of the explosion has not been confirmed.

Portugal has 196 soldiers in Afghanistan as part of a NATO-led international peacekeeping force in the war-ravaged country.

The soldiers are part of the International Security Assistance Force (ISAF) in Afghanistan and have helped guard the airport in Kabul, among other duties.

During a one-day visit to Portuguese troops stationed in the country on Monday, Defence Minister Luis Amado said Lisbon would reduce its peacekeeping contingent in Afghanistan after August 2006 because of budgetary restrictions.