High-speed trading firm Virtu Financial Inc. has indefinitely postponed its initial public offering plans, the Wall Street Journal reported, citing people familiar with the matter.

The move comes as high-frequency trading (HFT) is under intense scrutiny, following the release of author Michael Lewis' book "Flash Boys: A Wall Street Revolt".

Virtu's IPO, which was expected in April, was seeking to raise about $200 million to $250 million, valuing the firm at about $3 billion.

Reuters reported earlier this month that Virtu delayed the launch of its IPO as it awaited regulatory approval, which was expected within days rather than weeks.

Virtu, one of the biggest U.S. HFT firms, is active in making markets on IEX, taking the other side of trades to ensure the market stays liquid.