The rally planned by the opposition today is illegal because the organiser did not apply for a permit from the police.

Inspector-General of Police Tan Sri Ismail Omar warned that participants at the rally will be arrested.

"The organiser must comply with the Peaceful Assembly Act 2012. Marching without permit aimed at arousing anger is wrong according to the law.

"Comply with the law and use the correct channel to apply for permit from the district police chief," he told a press conference at Bukit Aman police headquarters here Tuesday.

Ismail said police will act against owners of social networking sites for trying to provoke racial sentiments following the general election (GE13) to prevent quarrels or chaos.

"Do not use social networking sites to incite and provoke as the police always monitor cyberspace," he said referring to allegations such as the blackout during vote counting and phantom voters involving the police.

The allegations posted online were later proven to be false.

Ismail also commented on the photograph of a group wearing black t-shirts, believed to be Malaysian students abroad, holding the Jalur Gemilang upside down.

"We monitor their action and will conduct investigation," he added.