US President Donald Trump was booed by sections of the crowd during Game 3 of the NBA Finals in New York on Monday, becoming the first sitting American president to attend the championship series.

Trump's appearance at the game between the New York Knicks and the San Antonio Spurs drew a mixed reaction, with some fans cheering while others loudly jeered as he was shown on arena screens.

The president waved to spectators and acknowledged the crowd before taking his seat courtside. Security was visibly heightened throughout the event.

The visit marked a historic moment for the NBA, as no sitting US president had previously attended an NBA Finals game. Trump's attendance comes amid a busy political schedule and ahead of key engagements in Washington.

Despite the reaction from some fans, the game proceeded without incident as basketball remained the main focus of the evening.