Here are 10 developments in this big story:
Loudspeakers remained switched off during azaan at several places in Maharashtra, including Parbhani, Osmanabad, Hingoli, parts of Jalna, Nanded, Nandurbar, Shirdi and Shrirampur. At some places, they were used on low volume.
About 250-260 MNS workers have been detained across the state. Mumbai police detained several MNS workers gathered outside Raj Thackeray's residence, officials sad. In Pune, eight MNS workers were detained, they said.
"I have been receiving calls from several parts of the state and outside. At many places, my party's workers have been detained and issued notices. Those who are following the law are being detained and those who don't are going scot-free," Mr Thackeray told the media. He said the issue is "not only about mosques and there are several temples with illegal loudspeakers".
The MNS chief stressed that this is "not a one-day issue". "If mosques don't follow guidelines, then Hanuman Chalisa will be played at double volume. Students and ill people suffer because of loudspeakers. Is your religion bigger than people?"
The Maharashtra government has made extensive preparations to maintain law and order. Leaves of police personnel have been cancelled and forces deployed in sensitive locations. Mumbai Police Commissioner Sanjay Pandey is visited various police stations areas to review the situation in the city, news agency ANI reported.
According to the Maharashtra Home Department, 135 out of the 1,140 mosques in Mumbai used loudspeakers before 6 am today. "Appropriate action should be taken against these 135 mosques that went against the orders of the Supreme Court of India," the Home Department said.
Aurangabad Police has registered a case against Mr Thackeray for allegedly delivering a provocative speech two days ago. Mumbai Police have issued a notice to the MNS chief under Section 149 of CrPC, invoked to prevent a cognizable offence.
In a statement tweeted last evening, Mr Thackeray reiterated his plans to play Hanuman Chalisa on loudspeakers near mosques where loudspeakers have not been removed.
Mr Thackeray has been asserting that his protest against loudspeakers is not on religious but on social grounds and that the recitations from mosques are leading to noise pollution.
The face-off between Mr Thackeray's party and the state government helmed by his cousin Uddhav Thackeray comes ahead of the civic elections in Maharashtra, in which the BJP is attempting to get the control of the Mumbai civic body. The ruling Shiv Sena has accused the MNS of being the "B Team" of the BJP, attempting to cut into the Sena votes with its aggressive stance on Hindutva.