A knife attack in the Portuguese seaside resort of Cascais on Wednesday morning left one tourist from the US dead and another seriously injured, according to local police.

A tourist from the United States was killed and another seriously injured in a knife attack on Wednesday morning in the Portuguese seaside resort of Cascais, located west of Lisbon, according to police.

A spokesperson for the Public Security Police (PSP) told AFP that "one of the tourists died at the scene and the other suffered deep wounds to their face and arm." No further details on the victims were immediately provided.

The assailants, three in number, fled the scene in a vehicle and remain at large. "We have circulated the necessary information throughout the entire PSP network to find the suspects," the police stated.

Following the attack, the injured victim was transferred to a hospital in the capital, Lisbon, as reported by Portuguese media.

The investigation into the incident has been transferred to the judicial authorities, with the case handed over to the public prosecutor's office and the criminal police.