WASHINGTON - Some US protesters smashed windows of stores and cars in Washington on Friday as Donald Trump is to be sworn in as the 45th US President.

About 500 anti-Trump protesters, many of whom are black-clad, marched through downtown Washington, holding banners including one saying "Make Racists Afraid Again."

Police in riot gear used stun grenades and pepper spray to disperse the protesters after they smashed windows of a local Bank of American branch, a Starbucks store, a McDonald restaurant and some cars by throwing stones, media reports said.

Earlier in the morning, many protesters tried to block several entrances into the Inaugural Parade route on the Pennsylvania Avenue, as many Trump supporters waited for checking in.

But most of the protests, which were organized by anti-Trump groups including the Disrupt J20 and the ANSWER Coalition, were peaceful amid heavy security.

Trump will be inaugurated as the 45th president of the United States at a swearing-in ceremony held at the Capitol Hill on Friday, which was attended by about 900,000 people.