Gen Sergei Surovikin, a deputy commander of Russia's armed forces in Ukraine, is "currently resting", according to a top Russian politician, adding to speculation that he has been detained by the Kremlin.
Gen Surovikin has not been since in public since the Wagner group's failed uprising last month when its leader, Yevgeny Prigozhin, moved his forces close to Moscow before sensationally backing down after a last-minute peace deal.
There have since been unconfirmed reports that Gen Surovikin was held for questioning over his role in the uprising, with a parliamentary official now seeming to confirm this.
Andrei Kartapolov, head of the State Duma Defence Committee, is heard saying in a video on social media: "Surovikin is currently resting. [He is] not available for now."
British military intelligence earlier said on social media that the Russian Chief of the General Staff, Gen Valery Gerasimov, had been seen in public for the first time since the failed mutiny.
Gen Gerasimov was on Monday seen being briefed by video link by Russian Aerospace Forces Chief of Staff Col Gen Viktor Afzalov, who is Gen Surovikin's deputy.
The Ministry of Defence claimed that this move – the first time of its kind since the outbreak of war – added "further weight to the hypothesis that Surovikin has been sidelined following the mutiny".
Gen Surovikin was reported to have good relations with Wagner and with Mr Prigozhin, who praised the general while regularly hurling abuse at Russia's military leadership.
Some reports claimed that had advance knowledge of the mutiny and that Russian authorities were checking whether he was complicit.
Meanwhile, Russia has rejected claims by Ukrainian military intelligence that members of the Wagner mercenary group tried to acquire nuclear devices during its failed mutiny last month.
Ukraine's head of military intelligence, Kyrylo Budanov, said, without providing evidence, that Wagner fighters had reached the Voronezh-45 nuclear facility on June 24.
He said they had intended to acquire small Soviet-era nuclear devices to “raise the stakes” in their mutiny, according to reports.
“The Kremlin has no such information,” spokesman Dmitry Peskov said when asked about Maj Gen Budanov's assertion that Wagner mercenaries had made it to the nuclear base to try to get nuclear devices.
“It looks like more misinformation,” Mr Peskov said.
Maj Gen Budanov did not provide evidence for his assertion and he declined to say what discussions, if any, had taken place with the US and other allies about the incident. He also did not say why the fighters subsequently withdrew.
Reuters reported that a source close to the Kremlin with military ties had corroborated parts of Maj Gen Budanov's account.
In response to whether Wagner forces reached the base and sought to acquire nuclear weapons, White House National Security Council spokesman Adam Hodge said: “We are not able to corroborate this report. We had no indication at any point that nuclear weapons or materials were at risk.
Russia on Tuesday launched kamikaze drone attacks on Kyiv and attacked the capital and the southern port of Odesa the previous night.
The Institute for the Study of War said that the drone attacks on port infrastructure had been carried out to disrupt the Black Sea grain deal, and was also a warning to Nato members against giving more military aid to Ukraine during the summit in Vilnius.
It also said that Russia may be threatening the Black Sea grain to send a message to the deal's original broker, Turkish President Recep Tayyip Erdogan, who was alos involved in the return of five Ukrainian Azovstal commanders on July 7.
