Microsoft is trying to prevent antivirus companies from offering their software for Windows 10, according to complaints filed in the European Union and Russia last week.

Following a complaint from antivirus software maker Kaspersky Labs, Russia's Federal Antimonopoly Service (FAS) opened an investigation into Microsoft's practices related to Windows Defender, the built-in antivirus software in Windows 10.

The Russian investigation claims Microsoft has reduced the timeframe for third-party developers to ensure their software is compatible with Windows 10 from two months to six days. If the software doesn't meet certain requirements within that timeframe, it's replaced with Windows Defender.

"Since 'Microsoft' itself develops antivirus software—Windows Defender that switches on automatically if third-party software fails to adapt to Windows 10 in due time—such actions lead to unreasonable advantages for 'Microsoft' on the software market," FAS Deputy Head Anatoly Golomolzin said in a statement. "Our task is to ensure equal conditions for all participants on this market."

Russian cybersecurity expert Eugene Kaspersky said his company, which is one of the largest third-party antivirus providers, has filed similar complaints with the EU.

"The trend is clear: Microsoft is gradually squeezing independent developers out of the Windows ecosystem," Kaspersky wrote in a blog post. He cited several troublesome aspects to how Windows 10 handles antivirus software, such as automatically deactivating third-party antivirus programs when users upgrade from a previous operating system.

Kaspersky also claimed that Windows Defender alerts users that it is turned off if they have a separate compatible antivirus product. The pop-up alert makes it easy for users to turn on Defender and uninstall their other program without realizing it, Kaspersky wrote.

Microsoft did not immediately respond to a request for comment on Kaspersky's claims and the Russian investigation. But the company on Friday boasted about Windows 10's built-in security capabilities, including increased detection and blocking in Windows Defender.

"Windows Defender, which is enabled by default, can respond to new threats faster using improved cloud protection and automatic sample submission features to block malware 'at first sight,'" Microsoft wrote in a blog post. "We've also improved Windows Defender's behavioral heuristics to help determine if a file is performing ransomware-related activities, and then detect and take action more quickly."