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.
Orange powder was seen near the edge of the green just short of the putting surface but second-round play continued without any delay at Royal Liverpool.
Just Stop Oil protesters have disrupted several major sporting events in England this year, including tennis' Wimbledon and the Ashes cricket test at Lord's.