Ukrainian President Petro Poroshenko has congratulated Donald Trump on having been sworn in as the 45th president of the United States.

"Ukraine congratulates Donald Trump on inauguration as 45th U.S. President," Poroshenko said on Twitter on Friday evening.

"Wishing success to fulfill noble goals of leading the free world," he said.

Trump's first term in office started earlier on Friday, after he had been sworn in as the 45th U.S. president.