Russia hit buildings and infrastructure around Ukraine in fresh strikes on Saturday night.
Ukraine's SBU military intelligence agency said officials embezzled millions of dollars under the guise of arms procurement.
Kyiv meanwhile accused Moscow of not providing evidence for its claims that a downed military aircraft was carrying prisoners of war.
Here's a look at the latest developments in Russia's war in Ukraine on Sunday, January 28:
Ukraine exposes military procurement corruption scheme
Ukrainian authorities uncovered corruption in the defense sector amounting to about $40 million (€37 million), Ukraine’s SBU security service said.
The SBU said officials signed a deal to purchase 100,000 mortar shells for the military and paid in advance, but no arms were ever provided.
It said an investigation "exposed officials of the Ministry of Defense and managers of arms supplier Lviv Arsenal, who stole nearly 1.5 billion hryvnias in the purchase of shells."
"According to the investigation, former and current high-ranking officials of the Ministry of Defense and heads of affiliated companies are involved in the embezzlement," the SBU added.
Legal proceedings have begun against five individuals allegedly involved in the scheme.
Corruption within the military has been a particularly sensitive issue in Ukraine as it tries to maintain wartime public morale and present its case to join the European Union.
Ukraine presses Russia on downed flight claims
Ukraine refuted Russia's claims that a downed military aircraft was carrying prisoners of war who were set to be sent home.
Kyrylo Budanov, chief of Ukraine's GUR military intelligence agency, said that Russia has not provided any evidence of corpses that would prove that POWs were onboard the flight.
"There are a number of factors that are unclear," Budanov said in an interview with state TV.
"First of all, they did not show fields covered with corpses and remains," he said
"If it happened as Russia claims, why does Russia ... continue to hide the bodies?"
Russia launches fresh wave of strikes on Ukraine
Russia bombarded Ukraine with missiles and drones once again on Saturday night.
Attacks were reported in a number of regions, including Kharkiv.
Zaporizhzhia military governor Yuri Malashko said infrastructure had been hit but did not elaborate.
"Enemy drones have attacked the regional center," he said.
Meanwhile, Poltava military governor Filip Pronin said two Russian ballistic missiles had hit an industrial site in Kremenchuk.
Earlier on Saturday, the Ukrainian military said Russia ramped up its efforts to capture Ukrainian towns.
"The occupying forces have significantly increased the number of attacks and assaults — for the second day in a row, the enemy has carried out 50 combat operations," Brigadier General Oleksandr Tarnavskyi wrote on his Telegram channel on Saturday.
Tarnavskyi said the frontline towns of Myrnohrad and Novohrodiivka had also been hit by Russian strikes recently.