Police lodged two FIRs against MNS activists, arrested six of them and registered some non-cognizable offences in several parts of the metropolis, officials said.
NCP, a coalition partner in the Congress-led government in the state, has denied that its workers were involved in the attack on Thackeray's convoy at Bhingar in Ahmednagar district last evening and dubbed the incident as "stage-managed".
Tension brewed in parts of Mumbai and adjoining Thane districts since the midnight attack on NCP office at Ambernath with MNS trying to enforce a bandh to protest the Bhingar incident.
Angry MNS workers burnt effigies of Deputy Chief Minister Ajit pawar and blackened his posters in some parts of the city.
Incidents of stone throwing were also reported from Khar, Antop Hill, Chembur, Kurla and Bandra, police said.
Six people were arrested by the Khar police in suburban Mumbai after they vandalized the NCP's office there, while in Antop Hill in Central Mumbai a case of stone pelting was registered against four persons all of whom are absconding.
Bandra police registered a Non-Cognizable offence against MNS workers after they allegedly tore NCP posters. In central suburb of Mulund, 11 people were detained for illegal assembly and sloganeering, police said, adding there was some stone pelting in Vikroli also.
Minor clashes were reported between activists of the two parties but there was no official confirmation.
A car and a bus were were also damaged by MNS workers.
Suspected NCP workers had hurled stones at Thackeray'sconvoy at Bhingar and waved black flags but nobody was injured.
NCP activists were furious at Thackeray's criticism of Pawar, nephew of party supremo Sharad Pawar, whom the MNS leader blamed for the severe drought in several parts of the state.
Thackeray had at a public meeting in Solapur recently attacked Pawar, who headed the water resources ministry between 1999 and 2009, for allegedly having failed to check water scarcity despite huge spendings on irrigation projects.
There have been allegations of a Rs 70,000 crore scam in the irrigation department, which has been with NCP since inception of Congress-NCP government in Maharashtra in 1999.
Amid mounting tension, MNS MLA from Ghatkopar Ram Kadam issued an open threat to NCP leaders and workers if they continued to target Thackeray.
"We know how to give tit for tat. We believe in replying in the language people choose to speak to us. They (NCP leaders) have forgotten that they have to move in Maharashtra.... Their homes are in Mumbai," he said while speaking to a TV news channel.
MNS leader in the legislative assembly Bala Nandgaonkar blamed NCP for the incidents.
"Raj saheb is on a state-wide tour (during which) he is bound to criticise the government and his opponents. Raj saheb targeted Ajit Pawar and he also responded. Such criticism is nothing new. However, throwing stones at our leader's convoy and women workers getting hurt in police lathi charge is simply not done," he said.
On the attack by his partymen at NCP office in Ambernath, Nandgaonkar said MNS workers had merely reacted to the action of the ruling party. "It is up to them to stop. Our's was a reaction to their action," he said.
NCP, however, rejected MNS charge that its workers were responsible for the attack on Thackeray's motorcade and asked its cadre not to get provoked.
State NCP president Madhukar Pichad said Maharashtra was reeling under drought and party workers should direct their energy towards constructive work to provide relief to the masses.
NCP spokesman Nawab Malik said the incident of stone pelting on Thackeray's convoy was a "managed event".
"Our workers did stage a demonstration and waved black flags at Raj's convoy to protest his derogatory remarks against our leaders at his Solapur rally," Malik said, adding the home department should act against those responsible for destruction of private and public property.
"NCP has no history of politics of destruction unlike the MNS which has mastered the art of misguiding the youth and making them anti-social elements," he said.