Left to right: Mohammed El-Baradei, Amr Moussa and Hamdeen Sabahi
Egypt was facing renewed political tensions on Thursday after three leading opposition figures, including a former head of the UN's nuclear watchdog, were placed under investigation for allegedly plotting to topple Mohammed Morsi, the Islamist president.
A judge is to investigate Mohammed El-Baradei, the ex-head of the International Atomic Energy Agency, along with the former foreign minister and Arab League chairman, Amr Moussa, and Hamdeen Sabahi, a former presidential candidate, over accusations that they campaigned to unseat Mr Morsi during a recent outbreak of unrest.
The announcement by the new chief prosecutor, Taalat Ibrahim Abdallah, who was appointed by Mr Morsi last month, will heighten concerns that the president and his Muslim Brotherhood backers intend to scapegoat political opponents.
It comes two days after a controversial new constitution – denounced by the secularist opposition as a route to sharia law and discriminatory against minorities and women – was officially declared to have been approved in a referendum.
The probe results from a complaint filed by a lawyer following a wave of protest that swept the country after Mr Morsi's adoption last month of sweeping powers – later revoked – that would have put him beyond legal challenge.
While not necessarily leading to criminal charges, the investigation of an internationally respected figure like Mr El-Baradei – who for several years spearheaded the IAEA's scrutiny of Iran's nuclear programme – will raise concerns that Egypt is lurching towards authoritarianism.
Emad Abu Ghazi, the secretary general of the opposition party Mr El-Baradei heads, said it showed "a tendency toward a police state and the attempt to eliminate political opponents".
The investigation was announced as the opposition National Salvation Front – to which the three belong – said it would consider an offer of talks with Mr Morsi. However, the front's spokesman, Hussein Abdel Ghani said it would enter only "real and effective" talks, and dismissed a forum set up by the president as "farcical".
Separately, the country's jailed former president, Hosni Mubarak, is to be admitted to hospital after his health suddenly deteriorated.
An army source said Mr Mubarak – who has been ailing for some time – would be transferred from a prison clinic to Maadi military hospital in a Cairo suburb.
The 84-year-old former president has already suffered a series of health episodes since being sentenced to life in prison this year for failing to prevent the killing of hundreds of protesters in the popular uprising that ended his 30 year rule in February 2011.
Shortly after his trial in June, he was taken to a prison hospital following what officials called a "health crisis". State media reported that he was clinically dead when he was admitted unconscious but doctors said he had fallen into a temporary coma.
He was taken to hospital again on December 19 for scans after injuring his head in a fall in a prison bathroom.