US President Donald Trump, speaks as he attends a meeting with EU leaders at the European Council, in Brussels, Belgium on Thursday May 25, 2017. Pool/Stephanie Lecocq via Associated Press

The acting US ambassador to the United Kingdom sent out a series of tweets on Sunday in response to Saturday's terrorist attacks, one of which appeared to challenge President Donald Trump's criticism of London mayor Sadiq Khan.

"It is with a heavy heart I offer my condolences and support to the people of the United Kingdom. America grieves with you," tweeted acting ambassador Lewis Lukens. "The response from emergency services, law enforcement & officials in Ldn–as well as ordinary Londoners–has been extraordinary," Lukens continued.

He concluded by praising Khan's leadership, tweeting, "I commend the strong leadership of the @MayorofLondon as he leads the city forward after this heinous attack."

—U.S. Embassy London (@USAinUK) June 4, 2017

Trump, who initially used the terrorist attacks to tout his travel ban and push the courts to reinstate it, slammed Khan earlier on Sunday. "At least 7 dead and 48 wounded in terror attack and Mayor of London says there is 'no reason to be alarmed!'" Trump tweeted.

Several critics pointed out that Trump had taken Khan's words out of context — the mayor said on Sunday that Londoners have "no reason to be alarmed" about the increased police presence in the city in the days following the attack.

"We are all shocked and angry today - but this is our city," Khan tweeted on Sunday. "We will never let these cowards win and we will never be cowed by terrorism."

Saturday's attack at London Bridge and Borough Market killed seven people and left dozens injured. All three attackers were fatally shot shortly after carrying out the attacks. Police conducted a series of raids following the incidents and arrested 12 people from the East London neighborhood, which is home to many Muslims. The identities of the attackers have not yet been released.