Baltimore has stood up to Donald Trump's remarks.

US President Donald Trump on Sunday countered the latest charges that he is racist and promoting a "hate agenda" to win reelection, following his attacks on a prominent black lawmaker and his constituency.

In a series of tweets, Trump on Saturday took aim at Democratic Representative Elijah Cummings, a high-profile critic of his administration whose district covers much of the majority black city of Baltimore, Maryland, whose murder rate makes it one of the most violent cities in the country.

After calling Cummings's district a "rat and rodent infested mess" where no one would choose to live, Trump insisted on Sunday that he was just telling things as they are.

"There is nothing wrong with bringing out the very obvious fact that Congressman Elijah Cummings has done a very poor job for his district and the City of Baltimore," Trump said, without providing evidence to support his claim.

Later in the day, he reiterated his criticism of the congressman, calling him "racist" and saying, "His radical 'oversight' is a joke!" -- a reference to Cummings's leadership of the House Oversight Committee, which has launched investigations into Trump administration policies.

Trump's diatribes ignited a storm of criticism and came less than two weeks after the House of Representatives condemned Trump for "racist" comments targeting four first-term Democratic congresswomen who are from ethnic minorities.

Baltimore has stood up to Trump's remarks, which Mayor Bernard "Jack" Young dubbed "completely unacceptable."

The Baltimore Sun newspaper penned an editorial saying it's "better to have some vermin living in your neighborhood than to be one," whil people on Twitter supported the city and criticized the president using the hashtags #WeAreBaltimore and #BaltimoreStrong.

Trump's remarks on Cummings and the congresswomen are seen as a calculated but risky appeal, both to the disgruntled white, blue-collar base that helped get him elected in 2016, and to other whites who haven't decided whom to support in next year's elections.

'Disgusting and racist'

Coming from anyone else, the president's comments would certainly spell political doom. Yet after Trump's tweets attacking the four non-white lawmakers known as the "Squad," his approval among Republicans rose five points to 72 percent in a Reuters-Ipsos poll.

One of the lawmakers, Rashida Tlaib, charged Sunday that Trump does not even care about doing things to help the country.

"Look, our president has a hate agenda. He doesn't have a policy agenda and that is what he falls down on," Tlaib said on CNN.

In an op-ed piece for The Washington Post late Friday, 148 African Americans who served under former president Barack Obama pledged their support for the four lawmakers "as well as all those currently under attack by President Trump."

Obama, who has rarely spoken out since leaving office in 2017, retweeted the piece on Saturday.

Backed by the Democratic leadership in the House of Representatives, Cummings has used his committee to launch investigations into the Trump administration, including its policies on undocumented migrants caught at the border with Mexico.

The president's Acting Chief of Staff Mick Mulvaney argued Sunday that Trump's attack on the congressman is justified because Cummings had criticized him and said things that were not true.

"I think the president's right to raise that it has absolutely zero to do with race," Mulvaney told Fox News.

But leading Democrats laid into Trump.

"The president is, as he usually is, or often is, disgusting and racist. He makes these charges with no base at all," said Congressman Jerry Nadler, chairman of the House Judiciary Committee.

Nadler said Trump is trying to divert attention from congressional probes into Russian election meddling and obstruction of justice by the president.

Presidential candidate Bernie Sanders reiterated his assertion that Trump is a racist: "That is a disgrace and that is why we're going to defeat this president," he told CNN.

Sanders also said he does not believe Trump's race-based strategy is going to work because "the American people understand that whether you're black, white, whether you're Latino, Asian American, Native American, we need an agenda that works for all of us."