An eight-year-old girl and a 56-year-old man have been killed after a plane crash landed on a beach near Lisbon, according to local media reports.

Eyewitnesses said sunbathers ran towards the sea as the light aircraft made an emergency landing on the packed beach at Caparica, 30 kilometres south of the Portuguese capital.

The child was enjoying a day at the beach with her parents, who were unhurt in the incident, eyewitnesses said.

The man who died had been sunbathing on a towel when the plane passed over his legs, they said.

No others on the beach were thought to have been hurt.

Sao Joao de Caparica beach is one of the closest to Lisbon and draws big crowds in August, when the Portuguese take their main summer holidays.

A plume of smoke can be seen billowing from the crash site ( Twitter/@nunoinverno) (Twitter/@nunoinverno)

The small aircraft, reportedly a Cessna carrying two people, appeared to be in difficulty and wobbled as it skimmed low over the sunbathers, scattering them and spreading panic on the beach, according to local media reports.

The bodies lay covered on the sand as police cordoned off the area.