The group tweeted: "Three Just Stop Oil Supporters have disrupted The British Open - they demand that the UK government halts all new oil and gas projects."

One of the players - believed to be American Billy Horschel - helped security remove the protesters after the incident, which happened at around 12.20pm.

Two men and two women were arrested at the scene on suspicion of conspiracy to commit criminal damage and public nuisance, police said.

The Open, one of golf's four majors, is taking place at the Royal Liverpool course.

Just Stop Oil identified two of the protesters as a community coordinator, 18, and a 19-year-old student.

"I'm disrupting The Open today, not because I want to, but as a young person, I feel I have no other choice," the 18-year-old said.

"This government is knowingly taking action that will kill hundreds of millions of people and destroy my future."

A spokesperson for Merseyside Police said: "A small amount of powder was discarded onto the playing surface and it was reported that one person had a smoke pyrotechnic.

"Two males and two females were quickly detained by both stewards and officers".

The force said in its statement that the powder was removed and play was uninterrupted.

It added: "Merseyside Police respects the right to protest and expression of views but antisocial, criminal behaviour or disorder will not be tolerated and will be dealt with robustly."

The four people arrested are being questioned in custody.

The protests follow other action by the group in London today, with Just Stop Oil saying about 160 people marched in 16 groups.

Just Stop Oil said members were taking action at locations including Hammersmith, Redbridge, King's Cross, Victoria, Whitechapel, Farringdon and Earl's Court.

A video tweeted by the group shows members of the public pushing them off the road at one location.

It's not the first time people have taken things into their own hands, with activists also manhandled on Monday when they again blocked roads in the capital.

The group has become well known for disrupting high-profile events to publicise its cause.

Two members ran on stage during The Proms recently, while confetti and jigsaw pieces were thrown on the courts at Wimbledon a few weeks ago.

England cricketer Jonny Bairstow also carried off a protester at the Ashes in June, and orange powder was thrown on a table at the snooker world championship in April.

New powers to crack down on activists came into force this month.

They give police new rights to move static protesters, such as those who attach themselves to objects or sit in the road.