Warsaw's liberal mayor Rafal Trzaskowski won a narrow victory in Poland's presidential election, according to an exit poll, but a second-round run-off with conservative historian Karol Nawrocki will be required in two weeks' time to decide the country's next president.

The mayor of Warsaw was poised for a narrow win over a pro-Donald Trump nationalist in the first round of Poland’s presidential election that is critical for the pro-European government’s agenda to undo years of populist rule.