Updated

Turkish President Recep Tayyip Erdogan is to set rejoin the ruling party he co-founded following his narrow victory in a referendum that expands the powers of the president's office.

Most of the constitutional changes approved in the April 16 referendum will come into force in 2019. However, an article removing a requirement for the president to be neutral and cut ties with their party came into effect immediately, allowing Erdogan to return to the Justice and Development Party in a ceremony on Tuesday.

Erdogan is expected to be re-elected as its chairman at a congress on May 21.

Critics fear that the new presidential system approved in the referendum will lead to a one-man rule. Supporters say they will usher in stability and more efficient government.