US President Donald Trump has denied being a racist after remarks he made about a black Democratic Congressman and the US city of Baltimore.
Mr Trump had attacked Rep Elijah Cummings, calling his majority-black Baltimore district a "disgusting, rat and rodent-infested mess".
Several leading Democrats, including House speaker Nancy Pelosi, criticised the president for his language.
Mr Trump deflected the criticism, accusing Mr Cummings of racism.
"There is nothing racist in stating plainly what most people already know, that Elijah Cummings has done a terrible job for the people of his district," the president wrote in one of several tweets on Sunday.
"Dems always play the race card when they are unable to win with facts," he wrote.
Mr Trump has previously turned accusations of racism back on those accusing him, without evidence. He did not offer any examples of Mr Cummings being racist.
As chairman of the House Oversight Committee, Mr Cummings has instigated a series of investigations into the Trump administration, including its handling of migrants at detention centres.
President Trump's remarks came just weeks after he was criticised for another tweet in which he told four Democratic Congresswomen - all women of colour - to "go back" to the "crime infested" places they came from.
All four Congresswomen - Alexandria Ocasio-Cortez, Rashida Tlaib, Ayanna Pressley, and Ilhan Omar - are American citizens. Three were born in the US, while one, Ilhan Omar, came to the US as a child refugee. Days later, at a rally in North Carolina, some of President's Trump's supporters chanted "send her back!", in reference to Ms Omar.
The president's description of Mr Cummings' Baltimore district, and his attacks on the four congresswomen, echoed similar language he had used in the past to describe mostly-black districts and African countries, which he reportedly called "shitholes".
A week before his inauguration in January 2017, Mr Trump lashed out at the black congressman and civil rights hero John Lewis, who had refused to attend his inauguration, calling Mr Lewis' district "crime infested".
What was the row with Cummings about?
A war of words began between the two men last week after Mr Trump said Mr Cummings was a "bully". He also took aim at his majority-black Baltimore district.
....As proven last week during a Congressional tour, the Border is clean, efficient & well run, just very crowded. Cumming District is a disgusting, rat and rodent infested mess. If he spent more time in Baltimore, maybe he could help clean up this very dangerous & filthy place— Donald J. Trump (@realDonaldTrump) July 27, 2019
In response, several Democrat lawmakers - including Ms Pelosi and presidential frontrunner Joe Biden - defended Mr Cummings and accused the president of racism.
.@RepCummings is a champion in the Congress and the country for civil rights and economic justice, a beloved leader in Baltimore, and deeply valued colleague. We all reject racist attacks against him and support his steadfast leadership. #ElijahCummingsIsAPatriot https://t.co/2LG8AuQrHh— Nancy Pelosi (@SpeakerPelosi) July 27, 2019
Mr Cummings responded in kind, tweeting: "It is my constitutional duty to conduct oversight of the Executive Branch. But, it is my moral duty to fight for my constituents."
How has Trump responded?
In a series of tweets, the president doubled down on his attacks on Mr Cummings and his Democrat colleagues.
"There is nothing racist in stating plainly what most people already know, that Elijah Cummings has done a terrible job for the people of his district," said Mr Trump.
He has also defended his economic record with "our Nation's great African American people."
....a look, the facts speak far louder than words! The Democrats always play the Race Card, when in fact they have done so little for our Nation’s great African American people. Now, lowest unemployment in U.S. history, and only getting better. Elijah Cummings has failed badly!— Donald J. Trump (@realDonaldTrump) July 28, 2019
Mr Trump also took aim at Democrat presidential candidate Bernie Sanders, who called Trump's latest remarks a "disgrace" during an interview with CNN.
The president highlighted that Mr Sanders compared west Baltimore to a "third world country" during a visit to the city in 2015.
"I assume that Bernie must now be labelled a racist, just as a Republican would if he used that term and standard!," he continued.
In an unexpected turn, Mr Trump launched an attack on civil rights activist Al Sharpton, who he claimed "Hates Whites & Cops!"
I have known Al for 25 years. Went to fights with him & Don King, always got along well. He “loved Trump!” He would ask me for favors often. Al is a con man, a troublemaker, always looking for a score. Just doing his thing. Must have intimidated Comcast/NBC. Hates Whites & Cops! https://t.co/ZwPZa0FWfN— Donald J. Trump (@realDonaldTrump) July 29, 2019
Rev Sharpton has previously criticised the president's comments about race, but had not spoken out about the latest exchange with Mr Cummings.
Responding to the tirade, Rev Sharpton posted a photo from 2006, saying that the president had a "different tune" now.
Trump at NAN Convention 2006 telling James Brown and Jesse Jackson why he respects my work. Different tune now. pic.twitter.com/mvNQmPdLUh— Reverend Al Sharpton (@TheRevAl) July 29, 2019
What is the situation in Baltimore?
Baltimore continues to face a number of problems, from gun violence to corruption.
In May, the city's Democratic mayor resigned amid investigations into business deals she made with city-linked public entities - the second mayor to resign in the last decade over corruption allegations.
Last year, a corruption scandal in the Baltimore police department saw eight officers convicted of robbing citizens and stealing pay.
And the city has one of the highest homicide rates in the US. There were 55.8 killings per 100,000 residents in 2017, up from 51.4 per 100,000 in 2016. New York City had 3.9 per 100,000 and Chicago had 28.07 per 100,000.
How have people reacted?
The response from Republican Party representatives was mostly muted.
In a statement, Maryland's Republican Governor Larry Hogan said "more attacks between politicians aren't going to get us anywhere".
The state's Lt Gov Boyd Rutherford, meanwhile, tweeted that he had "substantial policy differences" with Mr Cummings, but hoped the president's criticism was "not directed at the many good and hard working people who live in the district".
The hashtags #WeAreBaltimore and #WhitePeopleAgainstRacism briefly trended on Twitter, with thousands of social media users expressing opposition to Trump's remarks.
Among them was David Simon, a journalist and writer of The Wire, a critically-acclaimed American crime drama series set in Baltimore.
#WEAREBALTIMORE and there's a block party today on my southside street. This is a city of good Americans who deserve more than a grifting, hollow and self-absorbed failure of a man as their president. @realDonaldTrump is a permanent stain on our land. pic.twitter.com/sQAeE7pC1p— David Simon (@AoDespair) July 28, 2019
The Baltimore Sun newspaper also published a scathing editorial, calling Mr Trump "the most dishonest man to ever occupy the Oval Office".
"Better to have some vermin living in your neighbourhood than to be one," it added.