Electricity has been generated for the first time at what is expected to become the world's largest tidal energy farm.

The first of 269 underwater turbines was installed in the Pentland Firth last week and connected to the national grid using a subsea cable.

The turbines rely on the powerful tidal streams of the Firth to create electricity, similar to the way onshore turbines use wind.

Tim Cornelius, chief executive of developers Atlantis Resources, said: "This is the moment we have been working towards since we first identified the MeyGen site back in 2007.

"I am immensely proud of and grateful for the remarkable team of people who have contributed to this milestone.

"I look forward to bringing more news of the project development over the coming weeks and months as we move into the full operational phase."

Three more 1.5 mW turbines are ready to be installed in the Pentland Firth and the project is expected to generate about 400 mW in total when completed.

The project has been partly financed through a series of grants, including £23m from the Scottish Government.

A similar tidal project in Shetland became the first in the world to supply electricity to the national grid earlier this year.