Supporters of Egypt's deposed President Mohamed Morsi have staged fresh rallies, raising fears of renewed violence amid warnings from the interim government that police will disperse them soon.
Demonstrators began their marches after prayers on Friday, pouring out of several Cairo mosques and heading towards their key Rabaa al-Adawiya protest site.
They called for the reinstatement of Morsi after his removal by the Egyptian armed forces following massive protests against his rule and against his party, the Muslim Brotherhood.
On Friday, thousands of protesters chanted "down with [the Commander of Armed Forces] Sisi, Morsi is our president," as they waved Egyptian flags and posters of the deposed leader.
In the 6th October suburb of the capital, police fired tear gas in to disperse Morsi's supporters after they tried to storm the Media Production City, where satellite television channels are based, a security official told AFP news agency.
A security forces helicopter flew over head as ambulances sped into the area, and protesters threw gas cannisters back towards the police, an AFP correspondent said.
The latest demonstrations were a direct rebuke to authorities who have urged protesters to "let reason prevail" and end weeks-long rallies.
State television on Friday said security authorities will impose a siege over the protest camps Morsi's supporters, a step before clearing them.
The siege at two Cairo sit-in sites, Rabaa al-Adawiya and Nahda squares, will begin within 48 hours, Egypt TV reported. It said authorities will let people leave, but not allow anyone else in.
The stand-off raises fears of new violence. More than 250 people have been killed since Morsi's ouster.
International rights organisation Human Rights Watch on Friday warned of "bloodbath" if Egypt's interim leaders were to pro-Morsi rallies by force.
Situation 'very explosive'
Diplomatic efforts to avoid further violence have gathered pace, with the European Union's Middle East envoy Bernardino Leon and German Foreign Minister.
Guido Westerwelle both in Cairo to urge the rival camps to find common ground.
After meeting Brotherhood representatives, Westerwelle warned that the situation was "very explosive".
"We have seriously and adamantly pressured for a peaceful solution. I hope that those concerned have gotten the message," he said in a statement.
The US had also warned against further violence, with Secretary of State John Kerry saying in his interview that loss of life was "absolutely unacceptable". US Deputy Secretary of State William Burns was expected to arrive in Cairo on Friday night.
A senior member of the Freedom and Justice Party, the political arm of Morsi's Muslim Brotherhood, said the European envoys asked them to end their sit-ins.
"All the European delegates have the same message; they are pressuring the anti-coup protesters to disperse the sit-ins," said the official.
|Gehad el-Haddad, spokesman for Muslim Brotherhood, talks to Al Jazeera on Rabaa and Nahda sit-ins
In an interview with Al Jazeera, Gehad el-Haddad, the spokesman for Muslim Brotherhood, said: "Rabia (el-Adawiya Mosque) and Nahda (Square near the main campus of Cairo university) sit-ins are both peaceful assembly sit-ins by peaceful citizens, standing up for their democratic right. No one has the right to disperse them and any claims of using violence illegally to do so are the responsibility of the military coup, leadership and interim government. We hold them accountable for any bloodshed."
The Muslim Brotherhood on Friday criticised US' Kerry for saying the Egyptian military had been "restoring democracy" when it ousted Morsi, the strongest words of US support yet for the new leadership.
"We totally reject these statements and we are very disappointed in them," said Mohamed Ali Bishr, a senior Brotherhood leader and a minister in Morsi's former government.
"The United States is a country that speaks of democracy and human rights and they say something like that. I hope that they rethink their position and correct it," he told Reuters news agency.
Kerry later on Friday struck a more conciliatory tone, saying his country "will work very, very hard, together and with others, in order to bring parties together to find a peaceful resolution that grows the democracy and respects the rights of everybody."
Further raising tensions in the country, three top Brotherhood leaders, including Supreme Guide Mohamed Badie, are to be referred to trial for incitement to murder.
Egypt's interim government also faces an increase in attacks in the restive Sinai Peninsula, where gunmen on Thursday shot dead a policeman in the northern town of El-Arish.
Morsi himself has been formally remanded in custody on suspicion of offences when he broke out of prison during the 2011 revolt that toppled former president Hosni Mubarak.
He was detained hours after his ouster and is being held at an undisclosed location, where his family has been unable to see him.
EU foreign policy chief Catherine Ashton met Morsi on Tuesday, later telling reporters he was "well".