Earlier Friday, Yury Chaika, the 55-year-old justice minister until this morning, was endorsed by the upper chamber of parliament as the nation's top prosecutor.
Ustinov, 53, was removed from the prosecutor's office June 2 in what senior officials said at the time was a planned staff rotation bereft of political intrigue. Speculation soon followed that he would be given another senior position.
Putin said Ustinov had served six years as the top prosecutor and it was "a rather long term," adding that he had no claims against Ustinov.
Sergei Mironov, the speaker of the Federal Council, said after the move, "This was a technical decision and there was absolutely no political subtext. This is part of a personnel reshuffle that the president intends to carry out."
Ustinov's time in office was dominated by the Yukos case, which culminated in the virtual dismemberment of the oil company and the imprisonment of founder Mikhail Khodorkovsky, for tax evasion and fraud.