Elon Musk's controversial comments at the Unite the Kingdom rally in London have raised doubts over his fellowship of the Royal Society - the world's most prestigious scientific institution.

Addressing the rally organised by right-wing activist Tommy Robinson, Musk criticised "uncontrolled migration" and said: "Whether you choose violence or not, violence is coming to you. You either fight back or you die."

In response, Sir Adrian Smith, president of the Society, wrote a letter to fellows in which he raised concerns about "resorting to the language of violence" and the threat it posed to the organisation's values.

He said the matter would be discussed at the society's next council meeting.

Elon Musk was first elected a fellow of the UK's national academy of sciences in 2018, for his work in the space and electric vehicle industries. But his continued participation in the Royal Society has grown increasingly controversial.

Earlier this year, thousands of scientists signed a letter raising concerns about his involvement in funding cuts to US scientific research, as part of his previous role in Trump's Department of Government Efficiency.

The Society debated his fellowship in March but it was decided he would remain. Some fellows said any attempts to remove him could be seen as a curtailment of freedom of expression.

Without refencing Musk directly, Sir Adrian Smith wrote to fellows: "I am sure that many of you will share my concern at the events of the last week and the growing tendency to resort to the language of violence in pursuit of political programmes - including, unfortunately, an address to the recent London rally from a Fellow of the Royal Society."

He went on to say that: "Most of us have had the good fortune to have lived our lives in contexts where core values of tolerance, courtesy, respect for others, and freedom of speech have been widely acknowledged and respected and we have come to take them for granted."

"It is no accident that human understanding and science have also flourished to an extraordinary extent in this period. Threats to these values are now real," he finished.

Addressing the crowds on Saturday via video link, Musk said: "I think there's something beautiful about being British and what I see happening here is a destruction of Britain, initially a slow erosion but rapidly increasing erosion of Britain with massive uncontrolled migration.

"This is a message to the reasonable centre, the people who ordinarily wouldn't get involved in politics, who just want to live their lives.

"They don't want that, they're quiet, they just go about their business.

"My message is to them: if this continues, that violence is going to come to you, you will have no choice. You're in a fundamental situation here.

"Whether you choose violence or not, violence is coming to you. You either fight back or you die, that's the truth, I think."

Any decision to remove Mr Musk would be a significant moment in the organisation's history. It is 250 years since a member of the Royal Society was ejected: German scientist and writer Rudolf Erich Raspe, who was accused of theft and fraud.

Mr Musk has been approached for comment by BBC News sent via his companies Tesla and Space X.