Temporary road closures are in place around Whitehall, the police said. (File)

Roads were closed around British Prime Minister Theresa May's Downing Street office on Thursday as police investigated a suspicious item.

"Temporary road closures in place around Whitehall whist suspect item assessed," British police said in a Tweet. "Specialist officers are now in attendance."

A Reuters reporter at the scene said police were calmly directing tourists onto neighboring streets.