Move over Siri and Cortana - Facebook developing its own digital assistant for its Messenger service.

The personal digital assistant, called “M”, will be able to answer questions with live human help and perform tasks such as buying gifts online and booking restaurants.

Facebook's vice president of messaging products David Marcus said M was powered by artificial intelligence that's trained and supervised by people. In a post on his Facebook page, Mr Marcus said the service would be backed by a team of Facebook employees with customer service backgrounds who could also make travel arrangements and appointments.

That may give it an edge over rival services such as Google Now, Siri and Cortana, who all relay on technology to anwer queries.

The service is currently being tested by a group of a few hundred people in San Francisco.

Facebook has introduced several functions inside Messenger, which boasts more than 700 million users, to transform it into a standalone platform. Earlier this year, it rolled out games exclusively on Messenger and launched products for businesses to directly connect with consumers.

Additional reporting: agencies