Mauboy had the crowd dancing and singing along to her song "We Got Love".
Host of the UK's Eurovision broadcast, Graham Norton, was shocked by the disruption.
She was performing her track Storm dressed in a white asymmetric jumpsuit with flashing lights behind her as the audience sang along enthusiastically when an intruder snatched her microphone. If that isn't wonderful, I don't know what is.
SuRie remained on stage, clapping with the crowd, until she was given another microphone to complete her performance.
"We are not sure what is going to happen or whether we will get an opportunity to perform again".
The main favorite of Eurovision 2018 is Eleni Foureira, a singer from Cyprus, with the song Fuego, as William Hill bookmaker's office quotes demonstrate. Netta Barzilai, Israel's singer, with the song Toy is on the 2 place (index - 3,75).More news: Judge powers Yankees past Red Sox with late home run
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The 25-year-old accompanies the up-tempo song with trills, clucking sounds and chicken-like dance moves.
China have been banned from screening this year's final after one of its TV stations censored LGBT elements of Tuesday's semi-final, including Ireland's song Together, which included two male dancers depicting the end of a relationship.
Noway's Alexander Rybak is a previous Eurovision victor, but he seems unlikely to make it to the top a second time with his offering this year, That's How You Write A Song.
But Portugal - which hosting this year's event because its entry, Salvador Sobral, won with a restrained solo ballad last year in Ukraine - is putting on a show with stylish, elegant performances by a strong field of competitors.
Viewers and professional juries in all 43 participating countries will pick the victor, with televoting and juries each representing 50 percent of the outcome.