Tehran has warned neighbouring countries hosting U.S. troops that it would retaliate against American bases if Washington carries out threats to intervene in protests in Iran, a senior Iranian official told Reuters on Wednesday.

Three diplomats said some personnel had been advised to leave the main U.S. air base in the region, although there were no immediate signs of a large-scale evacuation of troops as took place in the hours before an Iranian missile attack last year.

U.S. President Donald Trump has threatened to intervene in support of protesters in Iran, where a rights group said 2,600 people have been killed in recent days in a crackdown on one of the biggest ever protest movements against clerical rule.

According to an Israeli assessment, Trump has decided to intervene, although the scope and timing of this action remains unclear, an Israeli official said.