U.S. President Barack Obama offers "whatever assistance is requested," after mine disaster in West Virginia that killed at least 25.

Obama gave his "deepest condolences" to families of the miners who died in the explosion at the Upper Big Branch Mine, nearly 50 km south of the state's capital Charleston, the deadliest mining disaster in the United States since 1984.

Obama made the remarks at an Easter prayer breakfast, saying there are still people missing at this moment, and rescue teams are searching.

Obama said he has told West Virginia Governor Joe Manchin "the federal government stands ready to offer whatever assistance is requested."