VIENNA (Reuters) - Austria's chancellor said on Sunday his country's intelligence agencies should have greater power to monitor communications on messaging apps to stop extremists after a planned suicide attack at a Taylor Swift concert in Vienna was thwarted this week.

Swift's three planned concerts were cancelled after Austrian authorities got wind of a plot led by a 19-year-old youth to launch an ISIS-inspired suicide attack at a soccer stadium where tens of thousands of fans were planning to attend the shows.

News of the planned attack has reanimated debate over the tight restrictions Austria has in comparison to other western nations on the monitoring of messaging communications just as the country gears up for an election on Sept. 29.

"We really need our agencies to be upgraded technically so they're on an equal footing with terrorists, with organised crime, so we can combat them," Chancellor Karl Nehammer said in an interview with Germany's Bild newpsper.

"It's vital that messenger services like WhatsApp, Signal, Telegram can be decrypted for security authorities, under judicial oversight, while upholding the rule of law," added Nehammer, who is seeking re-election next month.

Nehammer, who said Austria received a tip from a foreign intelligence service over the planned Swift attack, said the main suspects so far in the case had been captured.

But he spoke of more arrests being made as police continue investigations among criminal networks. More ISIS supporters had been identified, he said.

(Writing by Dave Graham; Editing by Angus MacSwan)