Police made a series of arrests early today after climate change campaigners boarded a coal freighter in a bid to prevent it unloading its cargo at a power station.
Environmental organisation Greenpeace claimed nine activists climbed on board the ship just after midnight as it travelled along the River Medway to the Kingsnorth Power Station in Kent.
The group used rigid inflatable speedboats to pull up alongside the vessel and attached climbing ladders to scale the 49ft (15m) hull.
Some of the group managed to scale the ship's funnel and foremast, while others were hanging off the side, a spokesman said.
The campaigners claimed they have enough food and water to allow them to remain on the vessel for several days.
There were also reports of three protesters swimming in the river in front of the vessel in an attempt to prevent it docking outside the power station.
This morning several campaigners remained on board, surrounded by officers.
A Greenpeace spokesman said today: "There are still five campaigners on the ship so the protest is continuing. They are going to try and hold their position for as long as they can to prevent the coal from being unloaded, but the ship is surrounded with police."
Kent Police said they received reports of protesters boarding a ship at around 10.50pm last night.
A total of five people were arrested over the protest and are being held at Medway police station.
A Kent Police spokeswoman said three men and one woman were arrested on suspicion of conspiring to commit criminal damage.
A second woman was arrested on suspicion of endangering an aircraft.
A statement from the force read: "Kent Police received reports of Greenpeace protesters boarding and attempting to impede the berthing of a coal vessel at Kingsnorth Power Station in Kent.
"Protesters used ribs (rigid inflatable boats) and also entered the water in order to board and prevent the coal vessel from making port.
"They were unsuccessful in their attempts and the coal vessel has now docked."
Chief Superintendent Matthew Nix said: "There are no reports of any injuries at this time. Public safety is of paramount importance to the operation and Kent Police is using all available resources to bring a safe conclusion to the incident."
One of the campaigners who managed to scale the ship's foremast said they were protesting against plans by energy giant E.ON to build a new coal-fired power plant at Kingsnorth.
Speaking earlier this morning, Sarah Shoraka, 31, said: "There are nine of us on the ship. We have split into three teams of three, with one team on foremast, another on the funnel and the third hanging off the side.
"We are using walkie-talkies to stay in contact with each other and have enough food and water to last several days.
"We will stay as long as we can to stop the coal being unloaded."
Ms Shoraka, who works for Greenpeace, went on: "Scientists are telling us we can't beat climate change if we keep burning coal, and yet (Climate Change Minister) Ed Miliband's new policies would still allow E.ON to build the dirtiest new power station in Britain for 30 years.
"The experts say we have the technologies we need to slash emissions and power Britain with renewable energy and more efficient use of cleaner fuels, it just needs the politicians to give them the green light.
"New coal plants that emit huge amounts of carbon can never be the answer."