Joe Biden has been sworn in as the 46th president of the United States amid heightened security and the ongoing COVID-19 pandemic. 

Biden, surrounded by his family, was given the oath of office by Chief Justice John Roberts at around noon on Wednesday, Eastern time, outside the U.S. Capitol. 

In his inaugural address, Biden said "this is democracy's day and a day of history and hope of renewal and resolve."

Biden called on Americans from all walks of life to join him in a quest for "unity," saying that the U.S. must end the uncivil war that pits red against blue, rural versus urban, conservative versus liberal.

Kamala Harris was sworn in as vice-president ahead of Biden. She is the first woman to serve in the post.   

Donald Trump, who has not formally conceded the presidency to Biden, skipped the inauguration ceremony in defiance of longstanding tradition.