Deputy head of human rights organisation, who became ill after being detained by security officials, convicted by court in Tehran

A prominent Iranian human rights activist who was taken seriously ill after being detained by the authorities has been sentenced to 11 years in jail.

Narges Mohammadi, 39, the deputy head of Iran's Defenders of Human Rights Centre (DHRC), a rights organisation presided over by the Nobel peace laureate Shirin Ebadi, was picked up last year by security officials who raided her house in middle of the night without a warrant for her arrest.

She was taken to Tehran's Evin prison where she was kept in solitary confinement but was released after a month and taken to hospital.

Mohammadi, a mother of two and winner of the 2009 Alexander Langer award for her human rights activities, has since developed an undiagnosed epilepsy-like disease which causes her to lose control over her muscles temporarily during the day.

It emerged on Tuesday that a court in Tehran has now convicted her on three charges: acting against the national security, membership of the DHRC and propaganda against the regime, for which she has received an 11-year sentence in total.

"I'm not involved in politics, I'm only a human rights activist," Mohammadi said by phone from Tehran. "I was informed of the 11-year sentence through my lawyers, who were given an unprecedented 23-page judgment issued by the court in which they repeatedly likened my human rights activities to attempts to topple the regime."

Mohammadi, who is also a member of Iran's National Peace Council, said she would appeal against the sentence.

In March, the International Campaign for Human Rights in Iran, a US-based non-governmental organisation, reported that security forces had stolen Mohammadi's medical records from the hospital. Her husband, Taghi Rahmani, a political activist, has spent a third of his life in jail.

Ebadi said Mohammadi's conviction showed Iran's judiciary was manipulated by intelligence and security officials.

"Whilst in jail, Mohammadi was threatened by her interrogator that she would be given at least 10 years if she did not cease her activities and now we see that the interrogator's prediction has come true," she said.

The British Foreign Office called on the Iranian government to overturn her "harsh" sentence . "[Her conviction] is another sad example of the Iranian authorities' attempts to silence brave human rights defenders," the FCO said. "She has done nothing but work for a human rights NGO under difficult circumstances to fight for the legitimate rights of the Iranian people."

Amnesty International also reacted with outrage to Mohammadi's conviction. "The verdict claims that Narges Mohammadi is a liar and has tarnished the image of Iran," said Drewery Dyke, Amnesty's researcher on Iran. "However, this latest verdict regrettably does exactly that by showing what Iran's judiciary thinks of the government's so-called commitment to uphold human rights in the country and indeed exactly how it deals with those advocating international human rights standards."

According to Amnesty, Mohammadi has campaigned for an end to death penalty for those convicted under the age of 18, for which she has long been targeted by the authorities.

Other human rights activists in Iran have also been sentenced to lengthy prison terms, including women's rights activist Shiva Nazar Ahari and lawyer Nasrin Sotoudeh, whose 11-year sentence was reduced to six years in an appeals court two weeks ago.