Thousands of protesters have marched in Britain's capital, London, against US President Donald Trump's order to ban nationals from seven majority-Muslim states from entering the United States.

The demonstration on Saturday, which marked the second round of UK protests against Trump in a week, came as a US federal judge in the city of Seattle blocked the order pending a review.

Called for by a coalition of Muslim and anti-racist groups, the rally drew thousands of people outside the US embassy in London.

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Protesters later marched towards parliament, channelling anger at Trump and the British prime minister, Theresa May, for her cordial relations with the US leader.

Many in the UK are resentful that May extended an invitation to Trump for a formal visit to the country during a meeting between the two leaders at the White House last week.

A parliamentary petition to bar Trump from visiting the UK has picked up more than 1.8 million signatures, while one supporting his visit has just less than 300,000.

UK members of parliament will debate the issue on February 20.

As with earlier demonstrations against Trump, many protesters chose to bypass the placards produced by organisers and instead opted to make their own.

Here are some of the homemade banners that were on display during Saturday's demonstration: