PORTLAND, OREGON (REUTERS) - Portland Mayor Ted Wheeler said he planned to move out of his apartment after people broke windows of the high-rise tower and set fires outside it on Monday and demanded that Wheeler resign over his handling of months of anti-racism protests in the Oregon city, according to a report.

In a Tuesday email, Wheeler told fellow residents of the apartment building in downtown Portland that it would be best for all their safety if he found a new home, the Oregonian newspaper reported on its website.

"I want to express my sincere apologies for the damage to our home and the fear that you are experiencing due to my position," according to a screenshot of the email sent to The Oregonian.

Wheeler's office did not immediately respond to a request for comment on Wednesday (Sept 2).

Portland has seen over 90 days of protests calling for policing and social justice reforms since the killing of George Floyd, a 46-year-old black man, in Minneapolis on May 25.

Demonstrators have gathered outside Wheeler's building calling for him to step down over police violence, including the use of tear gas and other munitions against demonstrators.

Police declared a riot on Monday and arrested 19 people as some graffitied the walls of Wheeler's apartment building, smashed windows and threw burning material inside, Portland Police said.

President Donald Trump has seized on civil unrest in Portland and other cities to criticise Democratic leaders like Wheeler and call for "law and order" ahead of the Nov 3 presidential election.

Wheeler, who has blamed Trump for stoking clashes, on Tuesday asked the city to join him in "denouncing violence" after a Trump supporter was shot dead in Portland on Saturday after taking part in a rally in support of the president.

"Everyone deserves to feel safe in their community," Wheeler wrote on Facebook.

"Last night saw more senseless violence in Portland."