(Reuters) - Microsoft Corp said on Tuesday its workplace messaging app, Teams, has more than 20 million daily active users, up from 13 million in July.

The software maker offers the app as part of some Office365 business packages, as well as a free version. Teams allows users to chat, share files, make calls and hold web video conferences.

Microsoft Teams, used by companies such as General Electric and SAP, competes with Slack Technologies Inc.

Slack, whose customers include Electronic Arts Inc and Nordstrom Inc, reported more than 10 million daily active users in the second quarter ended July 31.

Slack's shares fell 8.4% following the news, to $21.18. They are down 45% from the close of their first day of trade in June.

Microsoft Teams also competes with Workplace by Facebook Inc and Cisco Systems Inc's Webex Teams.

(Reporting by Ambhini Aishwarya in Bengaluru; Editing by Rashmi Aich and Clarence Fernandez)