Britain will review its security following the incursion of a suspected Chinese surveillance balloon into U.S. airspace earlier this month, Defence Secretary Ben Wallace said.

The United States shot down the balloon, which it said was being used to spy on it, and three further flying objects have since been downed by security forces over North America.

Beijing has said it was a weather balloon that had blown off course and accused the United States of overreacting.

“The UK and her allies will review what these airspace intrusions mean for our security. This development is another sign of how the global threat picture is changing for the worse,” Wallace told the Telegraph newspaper late on Sunday.

The Telegraph reported that the security review would be used to help decide whether changes need to be made to the surveillance of British airspace.

The spectacle of the Chinese balloon drifting over the United States caused political outrage in Washington and brought into sharp focus the challenge posed by China to the United States and its allies.

Asked on Sky News on Monday if it was possible Chinese spy balloons had already been used over Britain, junior transport minister Richard Holden said: “It is possible.”

“The government is concerned about what’s going on,” he said. “China is a hostile state and we need to be aware of that and the way it acts and behaves.”