About 95 tonnes of oil have been leaked into the North Sea from a BP platform, the company has said.

The leak is about two and a half times smaller than the biggest North Sea spill in recent years, at Shell’s Gannet platform off Aberdeen in 2011.

The spill from the Clair platform is being monitored from the air by plane which, combined with modelling, shows the oil moving away from land in a northerly direction.

“The most recent surveillance flight already indicates significant dispersal of the oil at the surface,” the company said in a statement.

The platform, 46 miles (75km) west of Shetland, was shut down following the spill on Sunday at about 10am. The leak was caused by a technical issue with a system designed to separate the mixed production fluids of water, oil and gas, the company said following an investigation.

BP believes that allowing the oil to disperse naturally at sea is the best way to deal with the spill, although other options have not been ruled out.

In a statement, it said: “The release was stopped within an hour once the issue had been identified and Clair production was taken offline.”

Oil spill and environmental experts from BP, Oil Spill Response Limited and the Department for Business, Energy and Industrial Strategy are said to have been working to assess any potential impact of the spill on the environment.

A spokesman for RSPB Scotland said: “There are currently many sensitive seabird species dispersing from their breeding colonies on Shetland and Norway out into the Atlantic, and these are potentially at risk. We need to know from BP and the maritime agencies exactly what type of oil has been spilled, if it is breaking up in the water column, and what the statutory conservation agencies are advising.

“It is critical that there is a full and open report of what has happened, with assurances that the situation will be monitored, and details of seabird concentrations in the vicinity revealed as soon as possible.”