There are multiple reports from Sydeny, Australia of a man with a shotgun holding hostages at the Lindt Chocolate Cafe in Martin Place:

And photos of the scene show what looks to be an ISIS flag:

Updates to follow.

Update 6:42:

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Flag translated as, “There is no God but Allah and Muhammad is the messenger of God.”

Correction 7:27:

Update 7:30:

Editor’s note: This post has been updated with additional tweets and the headline updated to reflect breaking news.