European and US diplomats have refused to apologise for walking out of a funeral on Sunday for the sister of Robert Mugabe after Zimbabwe's president made a speech attacking the West.

Charles Ray, the US ambassador to the country, said on Tuesday that he would not say sorry for walking out of the ceremony when Mugabe told Western nations to "go to hell" after alleging that they interfered in Zimbabwean affairs.

Ray, who was summoned to the foreign ministry along with other diplomats for an explanation, said he had followed normal diplomatic protocols in attending the funeral of Mugabe's sister Sabina, who died aged 80.

However, the ambassador told journalists at a news conference that when Mugabe began his remarks "it became clear to me ... that I was not welcome".

"When America is treated in the manner that it was treated on Sunday, by anyone, at any time, then I will react," Ray said.

Sanctions criticised

Attacking international sanctions on Zimbabwe during his funeral oration, Mugabe said: "They say 'remove so and so' - of course, they mean 'Mugabe must go before we can assist you'.

"To hell with them. Hell, hell, hell with them whoever told them they are above the people of Zimbabwe that they decide what Zimbabwe should be and by who it should be ruled."

Albrecht Conze, the German ambassador to Zimbabwe, said: "While we were paying our respects, Europeans and Americans were treated disrespectfully, and as we are representing them, we all felt that we had no other choice but to leave the venue."

On Tuesday, Barack Obama, the US president, criticised Mugabe and warned Africa not to repeat the mistakes that betrayed the hopes of an "independence generation," which included his own father.

"I'll be honest with you. I am heartbroken when I see what has happened in Zimbabwe," he said at a White House event to discuss the continent's future.

"I think Mugabe is an example of a leader who came in as a liberation fighter and, I'm just going to be very blunt, I do not see him serving his people well," Obama told the meeting in response to a question about sanctions.

The US is Zimbabwe's biggest aid donor.