Cairo - Supporters of Egypt's ousted president called for new protests on Monday, threatening to deepen the country's crisis as the EU foreign policy chief met both the government and the opposition.
The Anti-Coup Alliance of Islamist groups organising protests against the ousting of president Mohammed Morsi urged demonstrators to march on security buildings on Monday night and called a million-man march for Tuesday.
Their statement came after the National Defence Council warned late on Sunday it would take "decisive and firm action" against demonstrators if they went beyond their right to peaceful protest.
Tensions were running high after the deaths of 72 people at a pro-Morsi rally in Cairo on Saturday.
A security source said on Monday that a police officer had died of wounds sustained in the violence.
"We... call for a million person march under the banner of 'Martyrs of the Coup' on Tuesday," the Anti-Coup Alliance said in a statement.
The group urged Egyptians "to go out into the streets and squares, to regain their freedom and dignity - that are being usurped by the bloody coup - and for the rights of the martyrs assassinated by its bullets".
It also called for protesters to march on security buildings across Egypt on Monday night "to condemn the criminal acts and the firing of live ammunition by the interior ministry at peaceful demonstrators".
The calls raised the possibility of fresh confrontations after the National Defence Council warned protesters "not to exceed their rights to peaceful, responsible expression of their opinions".
The council, which includes the military-installed interim president and the army chief, said demonstrators would face "decisive and firm decisions and actions in response to any violations".
The military issued its own warning to Cairo protesters in flyers dropped from helicopters early on Monday.
"We call on you not to approach military facilities or units, help us to protect your safety," it said, addressing protesters as "honourable sons of the nation".
With tensions rising, EU foreign policy chief Catherine Ashton met government and opposition figures.
Shortly after arriving on Sunday she met vice president for international affairs, Mohamed ElBaradei, his office said.
"ElBaradei stressed that Egyptian authorities are doing everything possible to achieve a peaceful way out of the crisis," a statement said.
She also held talks with interim president Adly Mansour, whose office said the discussions were "open and understanding", adding that the leader had "explained to her the exact situation the country is going through".
Ashton said earlier she would be calling for "a fully inclusive transition... including the Muslim Brotherhood", which she is set to meet later on Monday.
The group has insisted that it will not accept any solution to the crisis that does not involve Morsi's return to office.
The bloodshed in the Arab world's most populous nation has sparked mounting international concern, with UN leader Ban Ki-moon warning Egypt's interim leadership on Sunday that every death made it harder to end the crisis.
Ban "expressed his profound concern about the direction in which the transition in Egypt is moving" and condemned the heightened violence, UN spokesperson Morana Song said.
Protect all Egyptians
He urged the authorities to protect "all Egyptians, regardless of party affiliation", Song added.
A group of Egyptian NGOs issued a statement on Monday calling for interior minister Mohamed Ibrahim to be dismissed over what it called a "massacre," but also urged the Brotherhood to denounce violence.
"The interior minister should be dismissed and held accountable for his actions," the groups wrote, urging Morsi supporters to "take action to persuade their colleagues and leaders to renounce" violence.
In its first comments on the bloodshed, the interim presidency said on Sunday that it was "saddened" by the deaths, but dubbed the protest area where they occurred a "terror-originating spot".
A crackdown on Morsi supporters continued on Monday, with the arrest of two leaders of the moderate Islamist Wasat party - president Abul Ala Mady and vice president Essam Sultan.
State news agency Mena said they were being investigated on suspicion of inciting violence and murder.
The party has joined the protests calling for the reinstatement of Morsi, who has been in custody since just hours after his 3 July ousting.
Last week, he was formally charged with offences related to his escape from prison during the 2011 uprising that overthrew president Hosni Mubarak.
In the Sinai Peninsula, where security has deteriorated rapidly since the 2011 uprising, an overnight attack on a military post in Rafah near the border with Gaza killed one Egyptian soldier and wounded eight.