"The behavior of the Iranian regime poses an unacceptable threat to the UK and our partners," foreign minister David Cameron said in a statement.
The meeting in Tehran is designed to show that Hamas has the total support of Iran.
In the Sept. 30 crackdown, security forces killed at least 66 people, according to Amnesty International.
The Iranian Jewish community leaders' warning comes amid heightened tensions in Tehran ahead of the 1-year anniversary of the death of Mahsa Amini.
Hussein said he would visit Tehran on Wednesday to deliver the message in person in the hopes that it would prevent any escalation on the border.
The European Union's top diplomat Josep Borrell said on Tuesday that Johan Floderus' imprisonment had been raised repeatedly with authorities in the Islamic Republic.
Israeli authorities seem suspicious of Iranian involvement in the recent wave of attacks, Iranian state media has certainly taken a special interest.
Prince Faisal said the kingdom was keen to follow through with all main points of the China-brokered deal.
Neither the American nor the Iranian statement about the deal openly confirmed the payoff
The event in question was on the role of religion and human rights.