Karol Nawrocki, a right-winger backed by US President Donald Trump, has won Poland's presidential runoff, according to final results released on Monday - a result all but guaranteed to complicate relations with the European Union.

Karol Nawrocki, was expected to win the presidential election second round with 50.9% of votes, the news website Onet said early on Monday.

His rival, Rafal Trzaskowski, the liberal Warsaw mayor and an ally of the government led by Donald Tusk, got 49.11%.