Shetland coastguard were also alerted to the incident off of Scalloway Harbour, on Shetland’s west coast, at around 2pm.
Members of the public have been advised to stay indoors after a man was spotted carrying a gun on the boat earlier today.
A police spokeswoman said: “We are dealing with a firearms incident at the moment, it is on-going.”
She could not give any further details on the incident.
There was no need for a lifeboat to be deployed to Scalloway Harbour.
A Shetland coastguard spokesman said: “We didn’t actually task a life boat, there was a harbour port boat which was going to help but it was stood down.”
Shetland gunman: Shots reportedly fired at police by man in inflatable boat