In a veiled threat to splinter Sena group leader Raj Thackeray, blamed for the recent trouble in Mumbai, the police on Tuesday said it was mulling action against political leaders promoting enmity on grounds of region and language.

The state government and police promised stern action against guilty persons as the offices of famous Bhojpuri actor Manoj Tiwari and Congress leader Sanjay Nirupam were stoned in sporadic incidents of violence sparked by an anti-north Indian campaign by the Maharashtra Navnirman Sena for the third day in Mumbai on Tuesday.

Fresh arrests were made on Tuesday and they included Shiv Sena legislator Bala Nandgaonkar, but a close confidante of MNS chief Raj Thackeray, MNS spokesperson Shishir Shinde and senior functionary Yashwant Killedar besides MNS and Samajwadi Party activists, police said.

They were arrested in connection with the violence.

Congress spokesperson Sanjay Nirupam, who was earlier a Shiv Sena MP, was arrested along with 36 supporters at Shivaji Park in central Mumbai, before they could embark on a rally to Raj's residence.

A day after a first information report was filed by Samajwadi Party leader Amar Singh against MNS leader Raj Thackeray for alleged criminal intimidation, Joint Commissioner of Police (Law and Order) K L Prasad said, "We are analysing the statements made by leaders from the MNS as well as the Samajwadi Party recently and looking specifically for explicit statements on regionalism made by them."

The recent clashes are "as bad as the bomb blasts" witnessed in 2006, Prasad said.

Raj Thackeray also faced a case of criminal conspiracy filed by an activist from the Sharad Pawar-led Nationalist Congress Party before the Andheri metropolitan court.

Activist Munna Tripathi, who heads the Uttar Bhartiya Vikas Parishad, filed the case charging Raj Thackeray with criminal conspiracy, rioting with deadly weapons, promoting enmity between two groups and criminal intimidation.

Fuelling further tensions, Vasant Gite, a MNS corporator from Nashik, said his outfit will not allow trains coming from north India in Maharashtra if north Indian leaders do not stop from making allegedly provocative speeches.

Prasad said, "Actually, the action (against political leaders) was expected today itself but the advocate general was unwell due to which the action has been deferred to tomorrow." He however did not name any leader.

"If not arresting them, we can also serve notices on them asking them to observe restraint while making statements," said Prasad.

Prasad said instances of stone pelting were reported at the offices of Tiwari as well as of Nirupam at Andheri and a shoestore owned by an SP leader. Nine taxis were also damaged since Sunday, he said.

"We have arrested those caught for stone pelting and rioting for criminal conspiracy. MNS leaders were also a part of the same conspiracy. All of them were present in Dadar when the violence erupted on Sunday evening," Prasad said.

As many as 112 activists from the MNS and 19 from the Samajwadi Party have also been arrested since Sunday, Prasad added.