Officials said the two properties have been attached after the department issued a provisional order under the Benami Transactions Act, 1988, that came into force on November 1 last year.
They said the assets are in the benami or proxy-owned possession and the action has been taken after the department carried out raids in this case last month.
The value of the attached properties could not be ascertained immediately.
Benami properties are those in which the real beneficiary is not the one in whose name the property has been purchased. The officials added that a few more such assets will soon be attached in the case, even as they wanted to question Prasad's MP daughter Misa Bharti and her husband Shailesh Kumar.
Both Ms Bharti and her husband have skipped I-T summons in the past.
In this case, a chartered accountant, Rajesh Kumar Agrawal, allegedly linked to Ms Bharti and others, was also arrested by the Enforcement Directorate (ED) on May 22. Mr Agrawal is alleged to have aided in illegal transactions involving Mr Yadav's family.
The couple allegedly have links with a firm -- Ms Mishail Packers and Printers Private Limited -- which is suspected to have entered into benami deals for purchase of a farm house in Delhi's Bijwasan area.
Tax department officials had said Mr Yadav's kin held some of the properties under their scanner in a 'benami' way. The RJD chief said he was "not scared at all" and would continue to fight against "fascist forces".
"BJP mein himmat nahi hai ki Lalu ki awaz ko daba sake... Lalu ki awaz dabayenge to desh bhar me karoron Lalu khare ho jayenge... Main gidarbhabhki se nahi darne wala hoon (BJP does not have the courage to stifle my voice...If it tries to silence one Lalu, crores of Lalu will come forward. I am not scared of empty threats)," he had said in a series of tweets after the search operation.
The BJP had also accused Mr Yadav, Ms Bharti and his two sons Tejashwi and Tej Pratap, both ministers in the Bihar government, of involvement in corrupt land deals worth over Rs 1,000 crore, and asked the central government to probe one such transaction in Delhi.
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