The Syrian government has condemned Egypt's decision to cut ties with Damascus and back the armed uprising against President Bashar al-Assad's government, terming it an "irresponsible" move.
"The Syrian Arab Republic condemns this irresponsible position," an unnamed Syrian official told state news agency SANA on Sunday.
The official said Egyptian President Mohamed Morsi had joined the "conspiracy and incitement led by the United States and Israel against Syria by announcing the cutting of ties yesterday".
"Syria is confident that this decision does not represent the will of the Egyptian people," the official added, accusing Morsi of announcing the severing of ties to deflect attention from internal crises in Egypt.
A day earlier, Morsi had announced the "definitive" severing of ties with war-torn Syria, and the recall of Egypt's charge d'affaires in Damascus.
He also called for the international community to impose a no-fly zone and denounced the role of Lebanese armed group Hezbollah in Syria, where its members are helping the army battle rebels.
Meanwhile, Syria's neighbour Jordan also expressed concern at the rising violence in the country and possible repercussions on its own territory,
Jordan's King Abdullah II told graduating military cadets on Sunday that his country, a key US ally, was ready to fend off any Syrian threats.
Abdullah said Jordan, which hosts more than 500,000 Syrian refugees, "will emerge victorious in the face of all challenges, the way we always have in the past".
Abdullah's country is currently hosting multinational military exercises involving thousands of US troops. The US has also agreed to install Patriot missiles along Jordan's 375-kilometer border with Syria and is allowing a squadron of 12 to 24 F-16 fighter jets to remain after the exercises.
Cameron for opposition aid
Meanwhile, British Prime Minister David Cameron held talks on Sunday with Russian President Vladimir Putin on Syria's civil war, a meeting which could set the tone for the G8 summit, with the West at odds with Moscow over how to handle the conflict.
Cameron is seeking to forge a consensus as he hosts the leaders of the world's top industrialised nations in Lough Erne, Northern Ireland, from Monday.
In-depth coverage of escalating violence across Syria
Washington has upped the ante on Syria by vowing to send military aid to rebel forces battling to topple President Assad after saying it had proof that the government had crossed a "red line" by using chemical weapons on a small scale.
Ahead of his talks at Downing Street with Putin, Cameron said it was essential to assist the moderate rebels prepared to work with the West before fighters linked to al-Qaeda gained the upper hand in the opposition.
"I want to help the Syrian opposition to succeed and my argument is this: yes, there are elements of the Syrian opposition that are deeply unsavoury, that are very dangerous, very extremist, and I want nothing to do with them," he said.
"But there are elements of the Syrian opposition who want to see a free, democratic, pluralistic Syria that respects the rights of minorities, including Christians, and we should be working with them."
In Syria itself, the fighting is continuing, with Syrian state television and residents reporting that an explosion had shaken a Damascus neighbourhood housing several embassies and a military airport on Sunday night.
The UK-based Syrian Observatory for Human Rights (SOHR), an anti-government rights watchdog, said a car omb detonated at a checkpoint near the military airport in the western neighbourhood of Mezze. There were reports of casualties, but not confirmation on the number of those affected.
The media office of the Free Syrian Army, an umbrella group of armed rebels, confirmed that an explosion had targeted the military airport.
Earlier on Sunday, government forces shelled Ghouta, on the eastern outskirts of the capital. Activist videos also showed the Syrian army bombing the al-Asali district of Damascus, and intense fighting in al-Rastan in Homs.
In the village of Hatla, in the eastern Deir Ezzor province, amatuer video that emerged on Sunday showed armed fighters blowing up a Shia mosque. In a battle last week, more than 60 Shia fighters and civilians had been killed in violence between rebels and pro-government militias.
Al Jazeera's Andrew Simmons said that as tension escalated, rebel fighters and government forces had adopted stricter strategies and were no longer trading prisoners for money.
Adding in Egypt's move, and with the US and Russia remaining at odds on how to help solve the conflict, there is also "a diplomatic escalation," too, Simmons said.