The MNS Chief, responding to the summons in a case pertaining to the beleaguered IL&FS, reported at the ED office around 11 a.m.
All Maharashtra opposition parties like the Congress, Nationalist Congress Party, Swabhimani Shetkari Sanghatana, have come out in support of Thackeray, terming the ED move as "vendetta and witch-hunting".
Accompanied by his family members wife Sharmila, daughter Urvashi, son Amit and daughter-in-law Mitali and top party office-bearers, Thackeray left his home under a tight police escort for the ED headquarters in south Mumbai.
However, his family members and party leaders stayed put at the Grand Hotel nearby as no one was permitted inside the ED office.
Two days ago, in a statement, Raj Thackeray had declared that he would honour the summons by the ED.
Earlier in the day, MNS spokesperson Sandip Deshpande and other activists were detained in Dadar and later whisked off to the nearby Shivaji Park Police Station, while others were not allowed to leave their homes by the police to pre-empt any untoward incidents.
Strongly protesting against his detention, Deshpande termed it a "high-handed action" by the police.
Other activists protested silently by sporting black Tee-shirts with the slogan "EDiot Hitler" painted on them, as thousands of supporters came to Mumbai from all over Maharashtra to express solidarity with their chief.
Late on Wednesday, the MNS activists were served police notices warning them against creating any law and order issues on Thackeray's appearance before the ED.
The police have taken measures to maintain law and order in the city. Barricades have been put up, traffic diversions made and a large posse of police personnel and even a dog squad have been kept ready. Prohibitory orders have been issued in some key areas.
Thackeray has issued at least two direct appeals to all his followers to remain calm despite any provocation, keep away from the ED office, and desist from any form of agitation or violence.
In a surprise move, his estranged cousin and ruling ally Shiv Sena President Uddhav Thackeray on Wednesday indirectly backed Raj Thackeray by saying that nothing would emerge from his (Raj's) interrogation by the ED.
"I don't think there will be any outcome of his (Raj's) investigation by the ED," Uddhav had said.
Raj Thackeray's former business partners Unmesh Joshi son of former Lok Sabha Speaker Manohar Joshi and Rajan Shirodkar, have already been grilled by the ED in a case pertaining to the IL&FS imbroglio.
On Wednesday, agitated by the ED summons to the MNS Chief, a young party activist committed suicide by setting himself on fire.
( With inputs from IANS )