Obama: Trump keeps proving he's 'unfit' to be president

President Barack Obama has said Donald Trump is "unfit" to be president, during a press conference alongside Singapore's Prime Minister.

Mr Obama said that while he had had fundamental disagreements on policy with previous Republican presidents and Republican nominees, he had never thought they could not function as president.

The US president also questioned why Republican leaders continued to denounce Mr Trump's statements but were still endorsing him for president.