MADRID - A suspected gas explosion wounded at least seven people at a Japanese restaurant in the northeastern Spanish city of Tarragona on Sunday, officials said.

The blast happened at around 4pm local time when the restaurant was closed, Pau Ricoma, mayor of Tarragona, told reporters.

"Two people who were passing by were hurt," he told local media.

In all, seven people were injured, two seriously.

All were taken to hospital.

"It is not clear what caused the explosion but it is almost certainly gas," Ricoma said.

The Mossos d'Escuadra, the Catalan regional police, have opened an investigation. REUTERS