Around 20,000 policemen including State Reserved Police Force and CRPF personnel have been deployed across the city following incidents of stone pelting and violence by alleged MNS activists in suburban Mulund, Thane, Navi Mumbai, Borivali, Parel and Tardeo areas, police said.

Miscreants attacked a toll booth located in the north-east suburb of Mulund and set one of the counters on fire, police said.

Vandals targeted about 25 to 30 taxis parked in the Tardeo area of South Mumbai this morning and broke their windscreens, they said.

Also, two separate incidents were reported in the north west suburb of Borivali where some miscreants attempted to burn trucks, police said, adding they also tried to set an autorickshaw on fire in the suburbs.

Some MNS activists also allegedly tried to block roads in neighbouring Navi Mumbai but were prevented from doing so, police said.

Meanwhile, heavy police force has been deployed near the Bandra court as well as Shivaji Park area in Central Mumbai, which houses Raj's residence and MNS headquarters, they said.

The city also witnessed heavy patrolling at prominent roads in south central Mumbai and areas like Naigaon, Lalbaug, Parel, police added.

MNS chief Raj Thackeray was arrested on the wee hours of Tuesday morning for his alleged involvement in the attack on north Indian candidates appearing for a railway recruitment examination.

A case was registered against Raj and MNS activists for their alleged involvement in the attack on north Indian candidates appearing for a recruitment exam conducted by the Railways in suburb Kherwadi, city Police Commissioner Hasan Gaffoor said.

"We did not know whether he would come back to the city or not. Therefore the arrest in Ratnagiri," he said.

MNS activists involved in the attempted assault on candidates have also been arrested and police custody would be sought for all of them, the Commissioner said.