TULA/MOSCOW. April 19 (Interfax) - The State Duma will investigate the origin of the Marches of Dissent, Speaker Boris Gryzlov said in Tula on Thursday.

"A working group will be formed to investigate who is behind these provocative acts and who is the sponsor," he said.

The group will be formed at the State Duma Council next Tuesday, Gryzlov said.

Meanwhile, the Russian Public Chamber has formed a similar group for investigating and monitoring public actions.

Acting group head Vladislav Grib said on Thursday they will start with an investigation into the events that happened during the Marches of Dissent in Moscow and St. Petersburg on April 14-15.

"Obviously, rights of citizens and journalists were breached and provocative acts happened during the marches. However, statements by law enforcers and party members were hasty. The events require more profound analysis," Grib said.

"In contrast to law enforcement officers and political organizations, the Public Chamber enjoys certain trust," he said.