MOSCOW, March 13 (RIA Novosti) – Russia’s former Defense Minister, Anatoly Serdyukov, has been cooperating for the first time in an investigation into his alleged complicity in misusing Defense Ministry assets to carry out expensive renovation work at a luxury summer house belonging to his brother-in-law, and has testified as a witness, Kommersant reported on Wednesday.

During five hours of questioning on Tuesday, Serdyukov was asked about the construction work at the Zhitnoye resort in the Volga River delta owned by Valery Puzikov, who is married to Serdyukov’s sister.

Investigators believe Serdyukov personally supervised construction work at the site, which was carried out by military personnel from a nearby Russian air defense test site. They estimate construction of a 6.7-kilometer (4.2 mile) road and landscaping work had cost the state some 15.5 million rubles ($503,750).

According to Kommersant, Serdykov, who had previously refused to answer investigators’ questions personally and gave only written statements about his suspected abuse of authority, agreed to cooperate with investigators after checks were conducted at his relatives’ premises.

His lawyer Genrikh Padva said Serdyukov has given “exhaustive testimony” proving he is “innocent of the crime,” Kommersant reported.

Serdyukov, who earlier described the home improvements as an "operational necessity," told investigators on Tuesday that in exchange for construction work, the Zhitnoye resort's owners had promised to remunerate the servicemen working there with discounted vacations.

However, there were no reports of military personnel subsequently vacationing at the luxury resort, Kommersant said. The Zhitnoye resort is a popular location for VIP guests, including Vladimir Putin and Dmitry Medvedev, who visited for a fishing trip in summer 2011.

The former defense minister and his closest friends were the most frequent guests at the resort, which is also known as “the ministry’s dacha,” the paper said.

Serdyukov was sacked last November following a separate investigation into suspected fraud totalling over 13 billion rubles ($433 mln) from the illegal sale of Russian Defense Ministry property involving the Oboronservis defense property services company.