The order issued in April isolated these four investigations. The cases were not closed, the prosecutor general’s office said in a statement, but the order blocked Mr. Horbatyuk from issuing subpoenas for evidence or interviewing witnesses.

“We have no authority to continue our investigation,” Mr. Horbatyuk said in an interview.

One inquiry dealt with possible money laundering in a single $750,000 payment to Mr. Manafort from a Ukrainian shell company. The payment formed one part of the multimillion dollar transfers to Mr. Manafort from politicians in Ukraine that underpin indictments filed by Mr. Mueller in federal court in Washington and Virginia. Before the case was frozen, prosecutors had subpoenaed records from Ukrainian banks.

Another concerned a former chairman of the Ukrainian Parliament’s foreign relations committee, Vitaly Kalyuzhny, who had signed nine of 22 entries designated for Mr. Manafort in a secret ledger of political payoffs uncovered after the 2014 revolution. The ledger showed payouts totaling $12.5 million for Mr. Manafort.

The handwritten accounting document, called in Ukraine the Black Ledger, is an evidential linchpin for investigating corruption in the former government. Mr. Manafort denied receiving under-the-table payments from the party and his spokesman said the ledger might be a forgery.

The other two cases looked at Skadden Arps, which wrote a report with Mr. Manafort’s participation that was widely seen as whitewashing the politically motivated arrest and imprisonment of Mr. Yanukovych’s principal rival, Yulia V. Tymoshenko.

Two months before Ukraine’s government froze the cases, Mr. Horbatyuk reached out to Mr. Mueller’s office with a formal offer to cooperate by sharing evidence and leads. Mr. Horbatyuk said that he sent a letter in January and did not receive a reply, but that the offer was now moot, since he has lost the authority to investigate.