At least two people were killed and several injured in a knife attack at the Ismaili Centre in Lisbon on Tuesday, Portuguese police said.

An unidentified man carrying a large knife attacked the Shia Muslim centre in Lisbon just before 11 a.m. (1100 GMT) on Tuesday, a police statement said.

The attacker was shot after refusing to lay down his weapon and approaching officers with the knife. He was arrested and taken to hospital.

CNN Portugal said the alleged attacker was an Afghan national. Police did not immediately confirm his nationality.

A number of people looking distressed were standing outside the centre in Lisbon amid a heavy armed police presence and were later taken into the building.

Prime Minister Antonio Costa said everything indicated that it was an isolated act, and it was premature to make any interpretation about the crime.

Ismailis are a minority within Shia Islam whose members have been attacked by extremist groups in countries such as Pakistan.

Prince Karim Aga Khan, spiritual leader of the world's Ismailis, opened the centre in Lisbon in 1998, complete with prayer halls, classrooms, meeting rooms and exhibition spaces.

The Ismaili community in Portugal is one of the largest in continental Europe, numbering thousands, including many who fled Mozambique during its civil war.