Gambia's Vice President Isatou Njie Saidy, who has been in the role since 1997, has quit, a government source and a family member told Reuters on Thursday.
Saidy is the highest level official to abandon President Yahya Jammeh's camp in his stand-off with opposition leader Adama Barrow, who won an election in December.
Abubakar Senghore, Gambia's minister for higher education, has also quit, the sources said.