US President Donald Trump has said he is in "very good" health after completing "phase one" of his annual physical examination. The White House confirmed he underwent an exam and some laboratory tests on Saturday at Walter Reed Medical Center in Washington. The visit was not in the president's public schedule, and no details of the tests have been released. It comes 10 months after an annual exam found him "in very good health". In a statement, White House Press Secretary Stephanie Grisham said the latest tests were prompted by a "free weekend" in the president's diary, and that Mr Trump remained healthy and energetic without complaints. "Further speculation beyond the extensive and honest info I put out is wholly irresponsible and dangerous for the country," she added in a tweet. No set template is in place for the president's physical examination, but Mr Trump's last two were announced ahead of time and noted in his public diary. He has visited the Walter Reed Medical Center nine times since taking office. The 73-year-old is the oldest person to be sworn in for his first term as president, and the state of Mr Trump's health has attracted attention in the past. During his campaign he produced a letter that said he would be the "healthiest individual ever elected to the presidency". But the doctor named as its author later said Mr Trump had written the letter himself. His main Democratic rivals for next year's presidential race are also aged 70 or over, and personal health concerns have become a talking point on the campaign trail. Bernie Sanders underwent emergency surgery last month after suffering a heart attack. Former Vice-President Joe Biden, 76, has also pledged to release his medical records before voting begins.