Upping the ante in the "Mumbai for all" row, Shiv Sena supremo Bal Thackeray today ordered party cadres to greet Rahul Gandhi with black flags to mark their protests when he visits Mumbai tomorrow after the unfazed Congress leader stuck to his schedule.

Gearing up for the Congress leader's visit, authorities have tightened security at venues during his interactions with youths and slum dwellers even as Maharashtra Chief Minister Ashok Chavan warned of strict action if anyone takes law into their hands.

Bal Thackeray has asked Sena workers to show black flags to Rahul during his visit to the city, senior party leader Sanjay Raut told PTI.

Reacting with disdain, Congress spokesman Abhishek Singhvi said in New Delhi that Congress and Rahul are not bothered about Shiv Sena's rhetoric and their black flag protests.

Apparently setting the stage for a tough political war on the issue of North Indian migrants through the black flag protests, Bal Thackeray's directive came amid esclating war of words between Shiv Sena and Rahul who has taken that party head on with his remark that Mumbai is for all Indians and that all people have a right to go anywhere.

Against the backdrop of the personal and vicious attack by Shiv Sena leaders against Rahul and Bollywood star Shah Rukh Khan, who has also earned the ire of the party, Maharashtra Government has sought legal opinion on all controversial statements reported in the media in the last 15 days.

"We have asked the Law and Judiciary Department to check all the controversial visuals, statements that were reported in the media in last 15 days," Home Minister R R Patil said.