A tweet from former US president Barack Obama in response to the violent clashes in Charlottesville, Virginia, on the weekend has become the most liked of all time.

"No one is born hating another person because of the colour of his skin or his background or his religion," the tweet said.

It has been liked more than 3 million times since it was posted on August 13.

The tweet was part of a series of three tweets sent by Mr Obama, quoting late South African president Nelson Mandela's 1994 biography, Long Walk to Freedom.

"People must learn to hate, and if they can learn to hate, they can be taught to love ... For love comes more naturally to the human heart than its opposite," the other tweets said.

The most liked tweet was posted alongside a photo of Mr Obama visiting a day care facility in Maryland back in 2011.

His tweet came as US President Donald Trump was sharply criticised for waiting too long to condemn the white nationalist groups involved in the deadly clashes.

Mr Trump initially condemned "hatred, bigotry and violence on many sides", but on Monday bowed to mounting political pressure and spoke out against the hate groups involved.

But in a press conference on Tuesday he again said both sides were to blame, adding protesters on the political left violently attacked white nationalists.

A woman was killed when a car ploughed into anti-racism protesters who were confronting white supremacists in the Virginia college town, and dozens more were injured in the violence between the two groups.

Mr Obama beat singer Ariana Grande's tweet, sent after the Manchester bombing attack in May.

"Broken. From the bottom of my heart, I am so so sorry. I don't have words," her tweet, which has about 2.7 million likes, said.

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However, the tweet is not the most retweeted of all time.

That honour belongs to US teenager Carter Wilkerson, whose simple plea for a year's worth of chicken nuggets from US fast food chain Wendy's has racked up more than 3.65 million retweets.