May 2 (Reuters) - Ameren Corp posted a fall in first-quarter profit on Thursday, hurt by low demand due to milder weather in its service regions and a charge at its Missouri unit.

The utility reported quarterly income of $261 million, or 98 cents per share, compared to $264 million, or $1 per share in the year-ago quarter.

Utility firms often see reduced demand if their service regions experience moderate weather, putting them under pressure to reduce costs and expenses.

"We remain committed to disciplined cost management, which we expect to result in meaningful operations and maintenance expense reductions in the second half of the year," said CEO Martin Lyons.

Ameren reported an about 11.9% decline in its operating revenues to $1.82 billion during the quarter from a year ago.

Additionally, the company incurred a charge at Ameren Missouri related to its Rush Island Energy Center litigation, as part of its dispute with the Environmental Protection Agency over air pollution emissions.

The utility, which serves 2.4 million electric customers, reaffirmed its annual profit guidance between $4.52 and $4.72 on a per-share basis. (Reporting by Roshia Sabu and Saikeerthi in Bengaluru; Editing by Pooja Desai)