Germany warned its citizens to leave Iran, saying that there was a risk both of a sudden escalation in Tehran's existing tensions with Israel and that Germans might be at risk of arbitrary arrest in the country.

"In the current tensions, especially between Israel and Iran, there is a risk of a sudden escalation," the Foreign Office wrote in a fresh travel warning issued on Friday. "It cannot be excluded that air, land and sea transport routes could be affected," it added.

"German citizens are at concrete risk of being arbitrarily arrested and interrogated and being given long prison sentences. Dual citizens with Iranian and German nationality are especially at risk," the Foreign Office said.