A smoke flare has been set off at the Open Championship in Hoylake and orange powder thrown at the 17th green by Just Stop Oil protesters.
American golfer Billy Horschel intervened to help remove one woman before greenkeeping staff removed the powdered paint with leaf blowers.
"At around 12.20pm three Just Stop Oil supporters ran onto hole 17," said Just Stop Oil via a statement.
"They set off a smoke flare and threw orange powder paint on the green."
Three people were put in handcuffs and taken away by police officers.
It is understood police have now deployed one officer to each green on the course.
Open organisers were prepared for a protest, putting in extra security precautions and advising players to not engage with anyone who tried to disrupt play.
Just Stop Oil protesters have disrupted several sporting events in England this year, including tennis at Wimbledon and an Ashes cricket Test at Lord's.
England wicketkeeper Jonny Bairstow carried one pitch invader to the boundary at Lord's while three people ran onto a court at Wimbledon throwing orange paper and jigsaw pieces. There was also a protest at the snooker's World Championship, where a a man jumped on a table and dropped orange powder.