White House press secretary Karoline Leavitt announced on Friday that “deportation flights have begun,” four days after Donald Trump assumed office as U.S. 47th president.

The White House press secretary added that Mr Trump is sending a clear and strong message to the world.

Ms Leavitt, in a tweet on Friday, posted a photo of some person boarding a military aircraft, warning illegal immigrants in the U.S. of the consequences of their actions.

“Deportation flights have begun,” Ms Leavitt said. “President Trump is sending a strong and clear message to the entire world: if you illegally enter the United States of America, you will face severe consequences.”

In an interview with journalist Chris Cuomo on Friday, Tom Homan, U.S. border czar, said 1,300 criminals, some who have been through immigration courts, have been arrested.

“We’ve arrested 1,300 people, over a thousand of them are criminals,” Mr Homan said. “The other ones are either fugitives who’ve been through immigration court, that became a fugitive, or collaterals.”

Mr Trump had vowed to carry out the largest deportation of illegal immigrants in the U.S. during his presidential campaign.