Donald Trump has praised his own first 100 days in office, hailing his presidential efforts as "very productive".

Mr Trump became the first president since 1981 to snub the White House Correspondents' Dinner in Washington, instead attending a campaign-style rally in Harrisburg, Pennsylvania.

He began his speech with one of his familiar attacks on the news media, giving them a "big fat failing grade" and telling the crowd that they were "consoling each other in a hotel ballroom in our nation's capital right now".

"And I could not possibly be more thrilled to be more than 100 miles away from the Washington swamp, spending my evening with all of you and with a much, much larger crowd and much better people, right?"

He slammed CNN and MSNBC as "very fake news", before suggesting he might make it for the annual dinner in the future.

"Maybe we'll make it more exciting for them in Washington and show up next year, but we have good chance of showing up here again next year too."

The large crowd responded with cheers of "USA, USA, USA" as Mr Trump recited his now familiar themes, which include "making America great again", "draining the swamp" and building a wall between the US and its southern neighbour Mexico to stop illegal immigration.

He listed his achievements during the first 100 days of his presidency, including seeing a Supreme Court nominee confirmed by the Senate, pulling the US out of the Trans-Pacific Partnership trade accord, a rising stock market and the easing of regulations on exploration for energy.

"For the last 100 days my administration has been delivering every single day for the great citizens of our country, whether it's putting our coal miners back to work, protecting America's steel and aluminium workers - we love that steel and aluminium - or eliminating job-killing regulations, we are keeping one promise after another, and frankly the people are really happy about it, they see what's happening."

He repeated his plans to renegotiate the global climate deal signed by nearly 200 countries in 2015, something that may do little to placate the thousands of people who protested outside the White House hours earlier against his plans to dismantle the climate change legislation of predecessor Barack Obama.

He also warned the crowd to "get ready for the great, great battles to come" but added that "we will win in every case".