Mysterious radio signals coming from an unknown source 5.5 billion light years away have been observed live for the first time.

The fast radio bursts last just a few milliseconds, and just seven of these bright flashes have been discovered before – the first was found in 2007. All were found retroactively by looking through old data from the Parkes radio telescope in eastern Australia and the Arecibo telescope in Puerto Rico.

However, an international team of astronomers, led by Emily Petroff from the Swinburne University of Technology, have seen a radio burst in real time.

John Mulchaey, acting director of the Carnegie Observatories, said: "These events are one of the biggest mysteries in the Universe. Until now, astronomers were not able to catch one of these events in the act."

Petroff added: "These bursts were generally discovered weeks or months or even more than a decade after they happened! We're the first to catch one in real time."

Published in the Monthly Notices of the Royal Astronomical Society, the scientists mobilised 12 telescopes around the world and in space to capture the burst. After working out the burst location with the Parkes telescope, the others were used to make follow up observations on different wavelengths.

Daniele Malesani, astrophysicist at the University of Copenhagen, said: "Using the Swift space telescope we can observe light in the X-ray region and we saw two X-ray sources at that position. Then the two X-ray sources were observed using the Nordic Optical Telescope on La Palma."

Findings showed the source of the burst was located up to 5.5 billion light years from Earth.

However, the source of the radio bursts remain a mystery, the authors said. "We found out what it wasn't. The burst could have hurled out as much energy in a few milliseconds as the Sun does in an entire day," Malesani explained.

"But the fact that we did not see light in other wavelengths eliminates a number of astronomical phenomena that are associated with violent events such as gamma-ray bursts from exploding stars and supernovae, which were otherwise candidates for the burst."

Findings also suggest that the burst came from an area where there is a magnetic field because of the polarisation of light observed.

"The theories are now that the radio wave burst might be linked to a very compact type of object - such as neutron stars or black holes and the bursts could be connected to collisions or 'star quakes'. Now we know more about what we should be looking for," Malesani said.