Germany is looking into digital attacks by hackers targeting websites in the country.
The attacks - known as distributed denial-of-service (DDoS) - work by directing high volumes of internet traffic towards targeted servers in a bid by so-called "hacktivists" to knock them offline.
"The scope and source of these attacks are currently being clarified," said a spokesperson for Germany's interior ministry.
It comes on the same day outages were experienced by Microsoft users across the world.
Microsoft has not revealed how many were affected, but Downdetector.com, which tracks outages, recorded thousands of people reporting problems with Teams, Outlook, Microsoft 365 and XBox Live.
By later in the morning, Downdetector showed the number of reports had dropped considerably.
"We're continuing to monitor the recovery across the service and some customers are reporting mitigation," reported the Microsoft 365 Status Twitter account.
"We're also connecting the service to additional infrastructure to expedite the recovery process."
Outage reports for Teams were identified in the UK, India, Japan, Australia and the United Arab Emirates.
Many users were unable to exchange messages, join calls or use any features of the Teams application - forcing office workers to communicate in other ways.
Teams is used by more than 280 million people worldwide and forms an essential part of daily operations for businesses and schools, which use the service to make calls, schedule meetings and organise their workflow.
Microsoft Exchange Online, SharePoint Online and OneDrive for Business were also affected, according to the company's status page.
The company's cloud unit Azure also tweeted about the outage, and said that a subset of users had experienced problems with the platform.
Azure, which has 15 million corporate customers and over 500 million active users, revealed on its status page that its services were impacted across the globe.
The outage comes after Microsoft - which employs more than 220,000 people, including 6,000 in the UK - announced plans last week to make 10,000 job cuts across its global operations.