President Vladimir Putin has tapped a former colleague from the St. Petersburg Mayor's Office to replace Dmitry Kozak as the Cabinet chief of staff, the government's Rossiiskaya Gazeta reported Tuesday.

Sergei Naryshkin, 50, was most recently the deputy chief of staff of the Cabinet, a post he received when Kozak was named chief of staff in March and the two of them moved over to the White House to keep an eye on the new government of Prime Minister Mikhail Fradkov.

Kozak has been in the spotlight in the Kremlin, where he formerly headed the presidential administration, and in the White House due to his efforts to craft reforms to the country's public administration and judicial systems. Naryshkin, on the other hand, has maintained a rather low profile.

A biography of Naryshkin in Rossiiskaya Gazeta on Tuesday says he worked at one point as an expert for the State Committee on Science and Technologies in the Soviet Embassy in Belgium. According to Kommersant, however, Naryshkin was a KGB officer using the post as a cover.

Naryshkin worked from 1992 to 1995 in the St. Petersburg Mayor's Office under Putin's command. He then worked at Promstroibank in St. Petersburg until 1997.

He left to join the Leningrad regional administration in 1997, where he worked until early 2004, when Putin appointed him deputy head of the presidential administration's experts department.

Putin on Monday named Kozak his envoy to the Southern Federal District and the head of a new federal commision that will seek to improve living and education standards in the North Caucasus -- and in doing so tackle some of the root causes of terrorism in the region.