The sanctions have been put in place amid issues over non-payments to other clubs and local suppliers, report the Telegraph.
Hull Live say the reason for the embargo is a failure to pay a £1m loan fee to Aston Villa for Louie Barry.
Barry, who was previously linked with Boro, joined Hull on loan in January and spent the second half of the season on Humberside.
He was expected to join on a permanent deal this summer but talks with his representatives broke down this week.
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Hull will reportedly appeal the embargo, with the Tigers said to have paid the first instalment of the Barry loan fee, but Hull Live claims there are “growing concerns from suppliers both locally and nationally regarding the finances of the club and payment for goods”.
Hull’s owner Acun Ilicali has invested a huge amount of money since taking charge of the Tigers, but issues have arisen in recent months, with the Tigers failing to pay their players on time earlier this year.
Earlier this week, Ilicali is reported to have said at a fan forum event: “We don’t have financial problems. It’s true we are spending too much money.
“Sometimes you can have little technical problems. The club has loans, but those loans are to me. I will not ask for all the loans.”
Hull avoided relegation to League One on the final day of last season, with boss Ruben Selles later sacked. He has since replaced Chris Wilder at Sheffield United, with Bosnian manager Sergej Jakirovic having taken charge of the Tigers.
Jakirovic said at his unveiling this week: “I’m very much looking forward to seeing a better Hull City than we saw last season.
“My football philosophy is to adapt as soon as possible to the team, to develop them. I like attacking football, but we need such a profile of players. We will train always how we want to play. For me, this is the main sentence.
“During the training sessions, we will work a lot on build up through the middle zone to the finishing zone to create a lot of chances. I like high press, energy, intensity but we will see what the future brings.”
