In a thinly-veiled reference to the UK, EU chief Charles Michel said "respect for treaties, a basic principle of international law, comes to be considered optional even by those who, until recently, were its historical guarantors".
Tehran now wields considerable political and economic influence in neighbouring Iraq with some Iraqis deploring that their country was "handed over to Iran".
A senior US State Department official said Hezbollah stored chemicals that can be used to make explosives in several European countries.
The British-Iranian national, who has served four a half years of her a five-year sentence, faces new charges.
Zaghari-Ratcliffe appeared Tuesday morning before a branch of the country’s Revolutionary Court in Tehran, where she was first sentenced to prison on murky espionage charges in 2017.
Vigils for the victims of the Beirut blast were held in Tel Aviv, the Palestinian Territories, Tehran, Paris and London.
One F-15 fighter plane did briefly surveil the Iranian passenger jet from a safe distance but disengaged after it established it was a civilian aircraft, the US confirmed.