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

Parties that oppose the government of PM Donald Tusk did better than those that back him — creating a problem for Rafał Trzaskowski.

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.