Police have arrested a 12-year-old suspect after five pupils and one teacher have been injured in a mass stabbing at a school in Portugal.

It is not immediately clear what provoked the attack in the town of Azambuja - located 31 miles northeast of Lisbon.

One girl has been taken to a hospital in a serious condition, a duty police officer has said.

The other victims are not thought to have suffered life-threatening injuries.

Azambuja Mayor Silvino Lucio told CNN Portugal: "He entered (the school) after lunch and started stabbing everyone he saw."

It has been reported that the schoolgirl rushed to Santa Maria Hospital in a serious condition suffered chest and head injuries.

Others have injuries to their arms and stomach.