Israel is on high alert for the possibility of any US intervention in Iran as authorities there confront the biggest anti-government protests in years, according to three Israeli sources with knowledge of the matter.

President Donald Trump has repeatedly threatened to intervene in recent days and warned Iran’s rulers against using force against demonstrators.

On Saturday, Trump said the US stands “ready to help”.

The sources, who were present for Israeli security consultations over the weekend, did not elaborate on what Israel’s high-alert footing meant in practice.

Israel and Iran fought a 12-day war in June, in which the US joined Israel in launching air strikes.

In a phone call on Saturday, radical Israeli leader Benjamin Netanyahu and US Secretary of State Marco Rubio discussed the possibility of US intervention in Iran, according to an Israeli source who was present for the conversation.

A US official confirmed the two men spoke, but did not say what topics they discussed.

Israel has not signalled a desire to intervene in Iran as protests grip the country, with tensions between the two arch-foes high over Israeli concerns about Iran’s nuclear and ballistic missile programmes.

In an interview with The Economist published on Friday, Netanyahu said there would be horrible consequences for Iran if it were to attack Israel.

Alluding to the protests, he said: “Everything else, I think we should see what is happening inside Iran.“