The private airplane crashed after taking off from the small Tires airport, which is located near the resort town of Cascais about 20 km (12.5 miles) west of Lisbon and used mainly by private aircraft.
Andre Fernandes, a spokesman for the local emergency services, said the plane was headed for Marseilles in France. Everyone on board the plane, three French and one Swiss, died.
Another person on the ground died when the plane crashed into a truck, setting off a fire, Fernandes said. The cause of the accident was not yet known.
(Reporting By Axel Bugge, Editing by Toby Chopra)
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections.