A man holding a Turkish flag.

A defiant Turkish President Tayyip Erdogan denounced the West's "crusader mentality" on Monday after European monitors criticized a referendum to grant him sweeping new powers, which he won with a narrow victory laying bare the nation's divisions.

Supporters thronged the streets honking horns and waving flags, while opponents banged pots and pans in protest in their homes into the early morning. The main opposition party rejected the result and called for the vote to be annulled.