Egypt's cabinet Wednesday ordered a police crackdown on protests by ousted president Mohamed Morsi's loyalists, as European envoys headed for Cairo to try to ease tensions between the army-installed government and Islamists, AFP reports.
The order to the interior minister raised the prospect of a dangerous showdown just days after 82 people were killed at a pro-Morsi protest in Cairo.
It came as diplomatic efforts to find a peaceful way out of Egypt's crisis gathered pace, with the EU and Germany sending envoys to urge a peaceful resolution to the standoff.
Adding to the tensions, judicial sources said prosecutors had referred to trial the Muslim Brotherhood's fugitive supreme guide, Mohammed Badie, for allegedly inciting the killing of protesters.
The cabinet's announcement came in a statement that said pro-Morsi protest camps at two Cairo squares posed a "threat to national security".
It added: "The continuation of the dangerous situation in Rabaa al-Adawiya and Nahda squares, and consequent terrorism and road blockages, are no longer acceptable given the threat to national security."
The Islamists, camped out for weeks calling for the reinstatement of Morsi, Egypt's first democratically elected president, reacted defiantly.
The coalition of Islamists behind the protests called for a mass rally on Friday.
"Nothing will change," Gehad El-Haddad, a Brotherhood spokesman for the coalition, told AFP, dismissing the cabinet order as an "attempt to terrorise Egyptians".
Washington also expressed concern, urging Egypt to "respect the right of peaceful assemblies."
"That obviously includes sit-ins," State Department spokeswoman Marie Harf told reporters.
British Foreign Secretary William Hague called for "an urgent end to the current bloodshed" and the release of Morsi, in a phone call to Egypt's interim vice president Mohamed ElBaradei, Britain's Foreign Office said.
Amnesty International denounced the cabinet order as a "recipe for further bloodshed".
Hassiba Hadj Sahraoui, deputy director for Amnesty's Middle East section, said: "Given the Egyptian security forces' record of policing demonstrations with the routine use of excessive and unwarranted lethal force, this latest announcement gives a seal of approval to further abuse."
In Rabaa al-Adawiya, the mood was calm after the announcement. Thousands of people have been camped out in a protest tent city at the square.
The interior ministry had already warned that the demonstrations would be dispersed "soon," but without saying when or how.
Foreign trade minister Munir Fakhry Abdel Nur said Wednesday's statement did not "give room for interpretation".
Accusing the Morsi supporters of bearing arms, he told AFP: "It is clear the interior ministry has been given the green light to take the necessary measures within legal grounds."
Confrontations between Morsi loyalists and security forces have turned increasingly deadly, with 82 people killed in clashes with police on Saturday morning.
And at least 51 people were killed in earlier violence between demonstrators and soldiers outside Cairo's Republican Guard headquarters.
Brotherhood leaders, including supreme guide Badie, who is in hiding, are facing charges related to violence that preceded Morsi's ouster.
On Wednesday, judicial sources said Badie and jailed deputies Khairat al-Shater and Rashad Bayoumi had been referred to trial for inciting the killing of demonstrators, further weakening the already dim prospects for talks between the two sides.
The allegations relate to the deaths of protesters outside Brotherhood headquarters on the night of June 30.
Morsi himself has been detained on suspicion of involvement in prison breaks and the killing of policemen during the 2011 revolt that toppled president Hosni Mubarak.
The international community is stepping up efforts for a peaceful resolution to Egypt's stand-off.
An EU spokesman said Wednesday the bloc's Middle East envoy, Bernardino Leon, would be in Cairo later to continue mediation efforts. German Foreign Minister Guido Westerwelle arrived in Cairo on Wednesday evening.
In Washington, Senator Lindsey Graham said he and fellow Republican John McCain would head to Cairo next week at the White House's request.
President Barack Obama's administration has refrained from calling Morsi's overthrow a coup, a designation that would require the United States to halt its $1.5 billion in annual aid to Egypt.
On Wednesday, the Senate easily rejected a bid to end assistance by 86 votes to 14.
EU foreign policy chief Catherine Ashton left Cairo on Tuesday after her own mediation bid, but there was no indication her meetings had brought compromise any closer.
She met with several officials from the military-installed interim government and the opposition, as well as Morsi.
Her meeting with him at a secret location was the ousted leader's first announced visit, though the presidency said on Wednesday that an African Union delegation had also met Morsi.
"Morsi is well," she told reporters after the two-hour meeting with Morsi.
"He has access to information in terms of TV, newspapers, so we were able to talk about the situation and we were able to talk about the need to move forward."