Syria is behind the attacks on EU member state embassies in Damascus and Beirut, US and European diplomats are claiming.
Danish, Swedish, Norwegian and French embassies across the Middle East were attacked over the weekend as anger continues to rage about the publication of caricatures of the Prophet Muhammad.
"That does not happen by accident there has to be some kind of acceptance by the state to let that kind of demonstration to go ahead," US deputy secretary for European affairs, Kurt Volker told reporters on Monday.
"We hold Syria responsible for that," he added.
"If you look at the demonstrations in Lebanon, I think there are external forces at work."
Some of Lebanon's political leaders accused Syria of being behind an attack on the Danish embassy in Beirut over the weekend.
The mission was ransacked and burnt during violent protests.
Trouble spots
Meanwhile palestinian police had to break up a demonstration outside the EU’s offices in Gaza City.
Protesters smashed the windows of the German cultural centre and threw stones at the European Commission building.
Elsewhere, two Afghans were killed at a rally in the eastern city of Mihtarlam. Police fired on demonstrators after coming under attack.
The trouble began in September when Denmark's Jyllands-Posten published 12 caricatures lampooning Islamic intolerance.
The cartoons were published again by a Norwegian magazine last month.
Unjustifiable?
Describing the weekend’s events as "beyond what can be justified," Volker urged governments to recognise the importance of religious sensitivity.
"I think it is very important we are all politically sensitive and recognise what is objectionable. We are very sensitive about racism, racial epithets, we are very sensitive about ethnic conflict, I think we should equally sensitive on matters of religion," the senior US official said.
EU-wide reaction
The EU has condemned the violence as "utterly unacceptable" and national governments have stepped up accusations against Middle Eastern states for failing to stem the violent outbursts.
As holders of the EU's rotating presidency, Vienna waded into the international tussle on Monday.
"The presidency of the EU demands that all authorities concerned take the necessary measures to ensure the safety of European citizens and property."
In this moment of tension, the presidency of the EU urgently calls on all concerned to show restraint and to refrain from and prevent further violence," Vienna said in a statement.
"It is totally unacceptable that governments cannot secure embassies on their territory," Denmark’s foreign minister Per Stig Moller said on Sunday.
"What happened in Syria is completely unacceptable," added Norway’s Prime Minister Jens Stoltenberg.
"We are going to ask Syria for compensation and we will take the matter up at the UN."
Syrian foreign minister Faruk al-Chareh apologised for the attack on the Norwegian embassy in Damascus, while Lebanese home affairs minister Hassan Al Sabaa has resigned over attacks in Beirut.
Commission response
But the EU executive has repeated that it cannot issue an apology for the actions of the free press.
"We do not have the power to present excuses on behalf of the press," justice commissioner Franco Frattini has insisted.
"It would be a violation of the principle of freedom of the press."
Meanwhile, the EU’s foreign affairs head, Javier Solana has called for "mutual respect", saying that tolerance and sensitivity are just as important as freedom of expression.
"It is now time for everyone to act to calm the situation and to help consolidate the relationship of friendship and mutual respect sought by all the governments of the EU," he urged.
