A British-Iranian woman jailed in Iran spent one night in a clinic after experiencing "palpitations and panic attacks", her husband has said.
Richard Ratcliffe said tensions in Tehran, sparked by the US assassination of General Qassem Suleimani, are taking a toll on the mental health of his wife, Nazanin Zaghari-Ratcliffe.
Mrs Zaghari-Ratcliffe is midway through a five-year sentence, accused of spying, which she denies.
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The UK Government has been attempting to secure her release after affording her diplomatic protection in March 2019.
The 40-year-old is among as many as five people with dual British-Iranian nationality, or with UK connections, believed to be in prison in Iran at present.
Speaking on BBC Breakfast on Friday morning, Mr Ratcliffe said: "This is a situation where there is a lot of anger in Iran and a lot of vulnerability, and it's very stressful for the people involved.
"I mean, Nazanin was taken down to the clinic overnight two nights ago, through palpitations and panic attacks.
"So I think it's important for the Government to just do what they can."
He added: "She was put on beta blockers to calm down.
"We usually expect things to happen a week or 10 days later, so there is a sense of foreboding which is affecting all the prisoners."
Mr Ratcliffe added that he should be meeting Foreign and Commonwealth Office officials later on Friday.
He said: "There's certainly concerns, I think it's a very tough time, and you have heard on the news this morning about other events in Iran, it's just really sad.
"In terms of what contact we have had with the Government, we should be trying to meet with the Foreign Office today, in just a couple of hours' time.
"(We are) really pressing up on the media for a meeting with the Prime Minister.
"So we will be calling to find out when we can do that."
Mr Ratcliffe also urged Boris Johnson to pay a £400 million debt Britain owes Iran, as his wife now fears receiving a second jail sentence as Iran seeks revenge on the West.
The sum has been outstanding since pre-revolutionary Iran paid the UK for 1,500 Chieftain tanks in the 1970s.
The deal was cancelled after the Shah of Iran was deposed in 1979, but, while Iran has demanded the money back, Britain has so far refused.