Vegan environmental activists have blockaded a dairy distribution centre in Buckinghamshire, which they say handles 10% of the milk supply in the UK, while a dozen other activists have sought to occupy the headquarters of WWF.

About 50 activists from Animal Rebellion, a sister group to Extinction Rebellion, blocked the gates to the Arla distribution centre near Aylesbury, locking on to bamboo structures and concrete barricades to prevent lorries from gaining access.

Pictures circulated by the group showed activists locked on to at least one precarious bamboo structure, and others chained together beneath a van with a banner stretched across one side reading “Plant-based by 2025”.

They are demanding that Arla, a Denmark-based multinational food conglomerate with an annual turnover of about EUR10bn (GBP8.6bn), switches entirely to plant-based foods by 2025.

James Ozden, one of the group, said they began their direct action at about 5am, with activists walking into the Aylesbury site and assembling their lock-on structures. By 9am about 10 police officers had arrived, he said. Workers and drivers expecting to work from the site were standing around outside.

Ozden pointed to the recent IPCC report on the need for drastic action on greenhouse gas emissions “including methane, which is in large part a byproduct of animal farming”.

He said: “Companies like Arla claim to be leading the way in tackling the climate crisis, yet until these big multinationals start to talk seriously about the inevitable need to transition our food system to one that is plant-based, their words are empty.”

Arla said it was a farmers’ cooperative committed to producing dairy products in the most sustainable way possible, and that it intends to reach net zero emissions by 2050.

“We are working with the police to limit the impact of this demonstration to both our customers and those living locally to the site,” a spokesperson said. “We have managed to complete our morning shift changeover and all colleagues are safe; however, access to the site for our larger vehicles is being blocked.”

Later in the day, police in London drew batons against Extinction Rebellion protesters in an open top bus blocking the road at the south end of London Bridge.

The melee came as a protest march from City Hall reached London Bridge station, meeting the bus that had blocked the junction. In a step up in tactics from the Metropolitan police, officers climbed up to board the bus from the top, while their colleagues swung batons at protesters inside.

Previously police had sought to be more careful in making arrests when XR protesters have begun occupations, but in the past week officers have increasingly sought to nip such actions in the bud before they can take hold.

Elsewhere, a dozen activists affiliated with XR Youth Solidarity and WTF WWF occupied the headquarters of WWF in Woking at 9.30am. They said they were occupying the NGO’s offices in solidarity with indigenous groups in Tanzania, Cameroon and Kenya who they say are being evicted and persecuted by WWF’s conservation activities.

A spokesperson for the group said three activists initially gained access to the offices by posing as members of an environmental group. They then held the door open while others rushed inside with lock-on devices and overnight gear. They say they intended to hold the site for up to three days. Police had arrived, the spokesperson said.

“WTF WWF are occupying on behalf of indigenous Maasai communities living in Ngorongoro conservation area in Tanzania, Gbabandi, Cameroon’s Forest Indigenous Peoples’ Platform and the Sengwer indigenous people of Kenya,” the group said in a statement.

“WTF WWF is demanding that WWF UK challenge the mass evictions and human rights abuses being carried out in the pursuit of conservation against these indigenous groups.”

A number of other occupations and actions were expected around central London on Tuesday, the ninth day of Extinction Rebellion’s latest two-week action in the capital. Activists were asked to gather at City Hall, near Tower Bridge at midday for what was advertised as a “new occupation”. At the same time, a so-called “pram rebellion action” was expected to begin in Parliament Square. Just after 1pm, the XR Families group was expected to meet at St Paul’s cathedral for a “play-in and feed-in”.