Just Stop Oil protesters set off an orange flare next to the 17th green at the British Open on Friday before being driven off the course by the police in a golf buggy.
The incident happened as Corey Conners, Billy Horschel and Alex Noren walked up the fairway towards the green. American Horschel led a protester towards security officials and was cheered by other spectators.
Orange powder settled near the edge of the green just short of the putting surface but second-round play continued without any delay.
"A protester was quickly apprehended on the 17th hole and is one of four people who have been arrested by the police," organisers the R&A said in a statement.
"Play was not disrupted and we would like to thank marshals, players and other spectators for their vigilance and understanding as the protesters were removed."
Ground staff quickly cleared away the debris using leaf blowers.
Just Stop Oil protesters have disrupted several major sporting events in England this year including the Wimbledon Tennis Championships and the Ashes cricket test at Lord's.
Al Ain crushed 10-man Yokohama F Marinos 5-1 in the second leg of the Asian Champions League final on Saturday to register a 6-3 aggregate win and their first continental title in 21 years.
Fourteen-time French Open champion Rafa Nadal said there was still a chance this year's tournament in Paris may not be his last in comments ahead of his tough opener against fourth seed Alexander Zverev.
Outgoing Barcelona manager Xavi Hernandez said he was proud of his achievements with the club and was looking forward to being a fan again as he prepares to coach his final game against Sevilla.
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