LONDON — Nicola Sturgeon, the leader of the Scottish government and a powerful figure in the drive for Scottish independence, is expected to resign after more than eight years in the role, the BBC and other British news outlets reported. The announcement, which was unexpected, is to come at a news conference later on Wednesday morning.

The reasons for Ms. Sturgeon’s decision were not immediately clear, though she had recently been embroiled in a dispute over the Scottish government’s policy of gender self-declaration, which had erupted after a convicted rapist, Isla Bryson, was incarcerated in a women’s prison.

This is a developing story.