Around 20 climate change protesters have seriously disrupted operations at one of the UK's new generation of gas-fired power stations at West Burton in Nottinghamshire.

Police have made five arrests but overnight 11 protesters from the campaign group No Dash for Gas successfully scaled the middle of the plant's 91m (300ft) metal chimneys – the plant's water cooling towers – and another six have occupied a second one which was not yet in use, securing themselves on ledges.

One of the group tweeted exuberantly with accompanying pictures: "Guess where we woke up this morning! Dawn sun shining on other chimney where friends are perched on the ledge."

Speaking from the group's makeshift but sophisticated camp slung on the central chimney shortly before 1pm, one of them said: "We are settling in nicely. At the moment some of us are setting up a solar panel and there's a group fixing our portable loo. We've got a portable ledge lowered a short way down the flue with plenty of room for people to sleep on. EDF [the plant's operator] have assured us that the chimney had been shut down but we're still a bit worried about gases being around. But the plan is to stay up here with some of us in the flue to stop the furnace starting again."

Protesters up a water cooling tower at West Burton power station, blue tarpaulin highlighted. Photograph: Martin Wainwright for the Guardian

Ben Healey of No Dash For Gas said that the middle of the plant's three cooling towers had been working but had now shut down, with steam no longer pouring from its brim. He said: "There are nine activists up there and they have started abseiling down into the flue to prevent the furnaces being relit. That means we are in for the long haul.

"The six people on the other chimney, which is not yet fully built, have barricaded themselves in place and will be very difficult to dislodge."

The protesters said they had spent a busy night climbing the chimney and hauling up their equipment and food supplies to last at least a week.

The plant's owners and operators EDF confirmed that the middle tower had been closed down.

No Dash for Gas said that the action was aimed at stopping operations at the £600m power station that is one of a cluster of plants built around the site of the deserted medieval village of West Burton in the valley of the River Trent.

The group said: "West Burton power station is being targeted because it's one of the first in a new generation of highly polluting gas plants planned for the UK. The coalition government recently announced that it intends to give the green light to as many as 20 new gas plants – a move that would crash Britain's carbon targets, contribute to the climate crisis and push up bills."

In a statement, EDF said that the company was committed to low-carbon energy, adding: "The station is in a commissioning phase at the moment and the first unit is expected to be fully operational by the end of the year. While the protest is ongoing only essential staff are leaving and entering the plant. The protest will not affect supplies to energy users in the area or to the National Grid. Generation at the adjacent coal station is unaffected.

"We support the right to peaceful protest. However, any unlawful action is of serious concern and puts at risk the safety of the individuals involved. Our site management and security teams have taken the appropriate action in protecting the safety of the public, personnel and plant."

Nottinghamshire police said that access had been gained to the site by protesters at about 1.20am. A police spokesman said: "Around 10 are thought to have climbed the water towers and have secured themselves to restrict their removal. Searches are ongoing to find a number of other people who are also believed to have gained access to the site."

One of the protesters said a total of 17 people had climbed two towers roughly 80m apart. Speaking by mobile phone from the site, the woman, who gave her name as Ewa, confirmed the group was demonstrating against climate change and fuel poverty, as well as to highlight the need for renewable energy rather than "expensive and dirty" gas.

Ewa said: "Our motivation for this protest is to try and stop this government from locking us into a dependency on gas for the next 30 years. If billions can be found to bail out corrupt banks then billions can be found to fund a renewable energy economy."

Such an economy would create hundreds of thousands of green jobs, reduce household energy bills and benefit the environment, according to the protest group, who said they had sufficient supplies to stay at the power station for about one week.

Ewa said: "It's unusual that we are linking this directly to fuel poverty. We shouldn't be investing in any gas whatsoever."

Andrew Pendleton, head of campaigns at Friends of the Earth, said: "This morning's protest sends a powerful message that a new dash for gas is wrong – gas is the main reason our fuel bills have been rocketing, and staying hooked on it will cost us a fortune."

John Mann, the local Labour MP for Bassetlaw, said: "The protesters should clear off and get back down south. They are obviously people with a lot of time on their hands and they are not from this area. If they really practiced what they preached they would have walked to the plant. The local community have warmly welcomed the gas turbine development and it is the voice of these local people that count."

As drizzle moved in from the Lincolnshire wolds, the protestor called Ewa said: "Most of us are in the tarp shelter now with a few more on the platform slung inside the flue. We're keeping busy finishing the solar panel to power mobile phones and give us a bit of heat."

She said that the group was puzzled and disappointed by Mann's comments including his jibe about "clearing off back down south." She said: "We can't do that because quite a few of us are from the north-west and Yorkshire. We'll hope to win him over."

Local people said that a police helicopter with a searchlight had woken them at around 3am.

A couple on the nearest farm to the power complex, which had 600 acres compulsorily purchased when the coal-fired power station was built, were intrigued by the protesters' ingenuity.

"If the weather wasn't so wet, we could go and have a look in my micro light aircraft," said the farmer. "maybe I'll do that later this week." His neighbour, whose small holding is dwarfed by the old power stations' twin chimneys and cooling towers, said: "You get used to it. Our only complaint is that the coal trains wake my elderly Mum up at night."

Power generation at West Burton goes back to 1967 when the older coal-fired station that stands alongside the new plant was commissioned by Harold Wilson's Labour government.

Now a venerable complex with a discovery centre for local schools, it was due to be joined by a second coal-fired station but plans were cancelled when the electricity industry was privatised in 1990. Work started on the £600m combined cycle gas turbine station in 2008, with some 1,000 jobs involved in construction, including a 19km (12 mile) gas pipeline and generation equipment to supply power to about 1.5m homes and businesses.