MOSCOW (Reuters) - A Russian airline UTair Boeing 737 plane, carrying 78 passengers plus crew, has requested an emergency landing at the main airport in St. Petersburg, the company and a Russian aviation source said on Wednesday.

The source said one of the plane's engines had failed and that the plane had been due to land at 12:25 p.m. (0925 GMT)

Russia's Emergencies Ministry said it could not immediately comment.

(Reporting by Gleb Stolyarov, writing by Elizabeth Piper, editing by Timothy Heritage)