Former US President Barack Obama and his wife Michelle have agreed a book deal with Penguin Random House.

"The company has acquired world publication rights for two books, to be written by President and Mrs Obama respectively," the publisher said.

Titles and other details have not been disclosed but the deal is believed to be worth over $60m (£48m).

Mr Obama is the author of the bestsellers Dreams from My Father and The Audacity of Hope.

Mrs Obama has written American Grown - a book about food and gardening.

"With their words and their leadership, they changed the world, and every day, with the books we publish at Penguin Random House, we strive to do the same," Penguin Random House CEO Markus Dohle said.

"Now, we are very much looking forward to working together with President and Mrs Obama to make each of their books global publishing events of unprecedented scope and significance."