The Enforcement Directorate has registered a criminal case against controversial Islamic preacher Zakir Naik and his organisation IRF under money laundering laws.
The NIA has questioned around 20 associates of Naik, including his sister Nailah Naushad Noorani, in connection with its investigation, they said.
Two of the five Bangladeshi attackers, who hacked to death 20 people at a restaurant in Dhaka's diplomatic zone used to follow three controversial Islamists, including Indian Islamic preacher Zakir Nayek.
The IRF, in its plea, has challenged the November 17, 2016, notification of the ministry of home affairs which had imposed an immediate ban on the organisation under UAPA.
Britain and Canada have already banned Naik from visiting several years ago.
Home Minister also said CDs of Naik's speeches are being examined and asserted that the government will not compromise on the issue of terrorism.
The home ministry also ordered a probe by the Computer Emergency Response Team-India to ascertain whether there was hacking of government software systems as there have been several instances where licences of NGOs under scrutiny were renewed automatically.
In a four-page 'open letter' released in Mumbai, Naik posed five questions to the government.
They have been booked under Unlawful Activities (Prevention) Act and Indian Penal Code Section 120-B (criminal conspiracy), he said.
Holding that Naik's foundation's plea challenging the Centre's decision has "no merit", the court said the order of the government was "not arbitrary and illegal".
The National Investigation Agency carried out searches at the premises of controversial Islamic preacher Zakir Naik, his NGO and a few associates for the third consecutive day on Monday, even as it blocked the website of outlawed Islamic Research Foundation founded by him.
The action by the NIA came barely a few days after the Union Cabinet declared IRF as a banned organisation under UAPA.
Following the Centre's tough stand on Islamic preacher Zakir Naik's controversial comments on terrorism, nine teams from the National Intelligence Agency, the Intelligence Bureau and other agencies are scanning the former's activities, while special teams are scanning every footage of his speeches.
Controversial Islamic preacher Zakir Naik on Sunday claimed that there has been no misuse of funds by his banned NGO and rejected all allegations of involvement in terror-related activities.
In an open letter, Naik, 51, who is abroad, said he will pursue all legal options to get the ban repealed and that the judiciary will fail the Modi government in its 'plans'.
The 51-year-old televangelist, who is currently abroad, is being probed under terror and money-laundering charges by the NIA.
The controversial Islamic preacher also said that his remarks were being blown out of context and that he is a messenger of peace.
'Naik is an outcome of an image-centric Islam, which is linked to the technological changes introduced by new media.' 'English educated upper middle class Muslims embraced Naik's image-centric Islam in the 1990s.' 'Television converted him into a religious object.'