Chinese President Xi Jinping on Monday called his U.S. counterpart Barack Obama to offer condolences over the deadly shooting in Orlando, Florida.

On behalf of the Chinese government and the Chinese people, Xi expressed deep sympathy and sincere condolences to Obama, the U.S. government and the U.S. people. He also expressed grief to the victims of the terror attack.

At least 50 people were killed and 53 others wounded, including a police officer, early Sunday in a mass shooting at a popular gay nightclub in Orlando, Florida.

It has been the deadliest terror attack in U.S. history since the Sept. 11 terror attacks in 2001. The Islamic State has claimed responsibility for the shooting.