A five-year-old boy who was detained for five hours and reportedly handcuffed at Washington DC's Dulles Airport could have been "a threat to America", White House Press Secretary Sean Spicer has said.

The child was one of more than 100 people who were held across the country following President Donald Trump's executive order temporarily banning the entry of citizens from seven Muslim-majority countries from entering the US.

The order also suspended the US refugee admissions system for 120, but it emerged earlier that 872 refugees will be allowed into the country this week as denying them entry would cause "undue hardship".

The young boy detained at the airport on Saturday (28 January) was later identified as a US citizen living in Maryland by Senator Chris Van Hollen. In an emotional reunion with his mother, who is believed to have been born in Iran, the child is showered with kisses before being serenaded for his birthday.

Spicer was asked about the specific incident in a press briefing, to which he replied: "That's why we slow [the process] down a little."

He added: "To make sure that if they are a five-year-old, that maybe they're with their parents and they don't pose a threat. But to assume that just because of someone's age or gender or whatever that they don't pose a threat would be misguided and wrong."

Van Hollen hit back at the US president's controversial immigration restriction and tweeted: "This 5-yr-old U.S. citizen & Maryland resident is not a threat to our country. Donald Trump's executive order is." He added that the boy's mother had given the airport advance notice of his arrival, the Independent reported.

As outrage over the temporary ban grew, Trump fired the acting US attorney General Sally Yates on 30 January after she questioned the order's legality. Yates was replaced with Dana Boente, US attorney for the Eastern District of Virginia, who pledged to enforce the order.