France, June 2 -- A surprise presidential win for Poland's conservativeKarol Nawrockisignals potential clashes lie ahead with the pro-European government's reform agenda.

Polish nationalist opposition candidate Karol Nawrocki has narrowly clinched victory in the second round of Poland's presidential election, securing 50.89 percent of the vote.

Poland's electoral commission confirmed early on Monday, with the result marking a significant setback for the pro-European government's reform efforts.

His opponent, Warsaw's liberal mayor and former MEP Rafal Trzaskowski - a close ally of Prime Minister Donald Tusk's government - garnered 49.11 percent.

A closely watched exit poll on Sunday had suggested a slim win for Trzaskowski, adding an ...