Turkish police have detained the strongest rival to President Recep Tayyip Erdogan, a move that experts say is aimed at removing all possible contenders ahead of the next presidential election and further stretching his rule.

The moves against Istanbul Mayor Ekrem Imamoglu and dozens of others could help extend President Recep Tayyip Erdogan’s two decades in power.

The Turkish president's main political rival, Ekrem Imamoglu, was set to be nominated as his party's presidential candidate. His detention comes after he was stripped of his university diploma, disqualifying him.