A joint investigative team probing the August 31 unrest near the Ukrainian Verkhovna Rada building has obtained more evidence giving grounds to interpret them as preparations for and the organization of a terrorist attack, Ukrainian Prosecutor General Viktor Shokin said.

"The prosecutor general's information shows that the joint investigative team which was promptly set up yesterday in line with the president's instructions obtained more evidence giving grounds to qualify the offenders' actions yesterday as preparations for, the organization and the commission of an act of terrorism," the Ukrainian presidential press service said in commenting on a first report by security chiefs on an investigation into the August 31 events near the Rada.

Shokin also vowed that the investigation should be completed within the shortest possible time.

"There are four people who have been notified of being treated as suspects. A lot of other participants will be confronted with suspicions today or tomorrow," Shokin said, adding that "everyone will learn soon who ordered, plotted, and committed these crimes."