LONDON (Reuters) - Greenpeace activists boarded a ship arriving in Britain on Thursday to stop the delivery of more than 1,000 Volkswagen cars from Germany while others sought to immobilise vehicles at a port in anti-diesel protests.

VW admitted cheating diesel emissions tests in 2015, triggering political and consumer pressure that has caused a slump in sales of diesel cars in major markets, with governments announcing plans to ban vehicles powered by conventional combustion engines.

Greenpeace said its volunteers had boarded the ship in the Thames Estuary in an attempt to stop it unloading at the port of Sheerness in the southeast of England.

The ship had moved to an anchorage point off the coast of Margate on Thursday afternoon, VW said.

Two Greenpeace activists were still on board, having unfurled a banner with the words “Ditch Diesel” alongside an image of a young girl suffering from a respiratory illness, a spokesman for the environmental pressure group said.

Other protesters had earlier broken into a vehicle park at Sheerness to stick labels on engines and attempt to immobilise cars by taking the keys, Greenpeace said.

Most have now left but two remain on site, holding several thousand car keys, and will remain there until the ship returns to Germany, a spokesman said. VW confirmed that keys had been removed from some vehicles.

The carmaker also said that the majority of the roughly 1,200 cars on the boarded vessel were petrol rather than diesel models and that its vehicles meet stringent European regulations.

“The diesel vehicles, which are the subject of the protest, meet strict Euro-6 standards,” VW said in a statement.

Britain aims to ban the sale of diesel vehicles from 2040 -- replicating plans by France and cities such as Madrid, Mexico City and Athens -- as part of efforts to improve air quality, but activists said the measures needed to be implemented now.

“Diesel cars are toxic – so we’re here to block VW imports on behalf of all of the children who are the most acutely affected by the health impacts,” 38-year-old Janet Barker, who took part in the protest, said in a statement.

“The government says we need to wait another 23 years for dirty diesels to be banned. We can’t wait that long.”