Tehran slams Bern for intervening in country's 'internal affairs' with criticism of killings, use of picture of demonstrators outside Iran flying 'fake' pre-Islamic Revolution flag

Swiss Foreign Ministry in Bern says employee 'died in a fatal incident'; embassy represents US interests in Iran

Ignazio Cassis meets FM Zarif, also expected to meet President Rouhani

While FM Zarif initially responded angrily to encrypted American message sent to Swiss embassy in Tehran, subsequent communication between rivals was more measured

US president makes comment ahead of meeting with Swiss president, reportedly aimed at opening communications with Tehran