Turkish police have arrested Istanbul's mayor, Ekrem Imamoglu, a key rival of President Recep Tayyip Erdogan, as part of an investigation into alleged corruption and terror links. The arrest comes amid a crackdown on the opposition and dissenting voices in the country. In addition to the arrest, Turkey has imposed internet restrictions, blocking access to multiple social media platforms. Critics argue that the crackdown is politically motivated, following significant losses by Erdogan's ruling party in local elections. Imamoglu's party, the main opposition Republican People's Party, was set to choose him as its candidate in future presidential elections, but it is now unlikely that the vote will take place.