Addressing a gathering of thousands of Maharashtra Navnirman Sena (MNS) activists here, Thackeray warned of a "befitting reply" to rallies being held against the CAA and the NRC, and said "a morcha will be answered with a morcha, a stone with a stone and a sword with a sword".
In the afternoon, the MNS took out a huge march from Girgaum Chowpatty to Azad Maidan in south Mumbai demanding eviction of illegal Pakistani and Bangladeshi infiltrators.
The morcha was culminated at Azad Maidan.
After starting from his home in Dadar's Shivaji Park, Thackeray, wearing a saffron armband, visited famous Siddhivinayak temple in Prabhadevi, accompanied by his wife Sharmila and son Amit.
He joined the "mahamorcha" (mega march) on foot from Hindu Gymkhana and walked till Metro Junction, which is about one km apart, before asked by police officers to travel further in his car because of a huge crowd.
Addressing the gathering at Azad Maidan, the MNS chief said, "Today, anti-CAA and anti-NRC protests were given a befitting reply with this protest rally of the MNS. But let me warn you, next time morchas will be answered with morchas. And if you continue with your drama, stones will be answered with stones and swords with swords".
Thackeray, who had ran a vigorous campaign against the BJP and Prime Minister Narendra Modi during the Lok Sabha polls last year, had earlier defended the Citizenship (Amendment) Act and the National Register of Citizens (NRC).
Speaking at the rally, Thackeray wondered "opposition" by Muslims to the CAA and the NRC.
"I don't understand why Muslims are protesting against the CAA and the NRC. Who was going to evict those who are living in India since their birth?" he asked.
"...To whom are you (anti-CAA and anti-NRC protesters) trying to show your power, and why?" he said.
Thackeray blamed the ongoing protests against the CAA and the NRC on the "lack of proper understanding" of the issues.
"The CAA gives citizenship to those Hindus who have faced religious atrocities in neighbouring countries (Pakistan, Afghanistan and Bangladesh and migrated to India)," he said.
"..Do these people (illegal immigrants from Pakistan and Bangladesh) consider my county a 'dharmashala' (charity shelter)?" Thackeray questionned while speaking on the NRC.
He also wondered whether the Union government enacted the CAA and has proposed the NRC as a "ploy to divert the attention of people from the poor financial situation prevailing in the country".
He demanded "strict" implementation of the CAA and the NRC across the country.
In his speech, Thackeray appealed to the Central government to give a "free hand to the police for 48 hours to evict infiltrators from Mumbai, as it is useless to ask the state government".
"The issue of infiltrators is as important as that of drinking water, education and health. Pakistani and Bangaladeshi infiltrators should be thrown out from the country, and there shouldn't be any compromise on the issue," he told the gathering.
Apart from illegal Bangladeshi and Pakistani residents, a large number of Nigerians are also staying in Mira-Bhayandar region near Mumbai, where police also cannot enter their colonies, he said.
Knowing well that his push for the CAA and NRC might create a perception that he was trying to mend fences with the BJP, the MNS chief said, "These days, those who criticise the Union government are being labelled as anti-BJP and those praise it as BJP supporters. Isn't there any middle path?"
The MNS' Hindutva push came nearly two months after the Shiv Sena joined hands with the NCP and Congress to form a government in Maharashtra.
In early January, the MNS president met with former Maharashtra chief minister and senior BJP leader Devendra Fadnavis.
Days after, he replaced the old striped flag of the MNS and relaunched it in a new saffron avatar with the royal seal of Chhatrapati Shivaji.
Interestingly, eviction of illegal infiltrators has been a stated position of the Bhartiya Janata Party with which the MNS chief has had a love-and-hate relationship, since he turned into a Modi-baiter from being a supporter.
Throughout the day on Sunday, police maintained a strict vigil along the route of the march which was joined by MNS activists from Mumbai, its metropolitan region, and other parts of Maharashtra.
On the Azad Maidan dais, the MNS displayed photographs of Vinayak Damodar Savarkar, Dr Babasaheb Ambedakar, Savitribai Phule, and Thackeray's grandfather late Prabodhankar Thackeray.