Arab political figures and citizens condemned Israel's assault on the West Bank town of Ramallah on the day after Beirut's Arab summit put forward a plan for comprehensive Arab-Israeli peace.
Lebanon, which holds the summit presidency, issued a statement which called on the UN, US, Russia and the EU to halt Israel's "aggression".
The foreign ministry statement said: "What Israel is doing confirms again that it is a terrorist state which rejects peace."
Demonstrations erupted in the Lebanese capital and Palestinians in the Ain al-Hilweh refugee camp in south Lebanon burned tyres and condemned Israel's assault on the Palestinian President, Mr Yasser Arafat, which they called "an attempt to liquidate the Palestinian national cause by killing its foremost exponent".
There were also demonstrations in Syria and Jordan, where over half the population is of Palestinian origin.
The Popular Front for the Liberation of Palestine, speaking from Ramallah, warned the Arab world that Israel intended to kill Mr Arafat.
Mr Mounir Samaha, a Lebanese businessman, demanded: "How can the world stand by while women and children are slaughtered, while Israel destroys peoples homes and kills all chances of peace. We offer peace and Israel replies by waging war on innocent civilians. If Israel wants to live side by side with the Arabs, it must renounce its policy of force. But if Israel continues to make war on us like this, the Arab leaders will not be able to stand on the sidelines. They will have to send in troops if they want to stay in power."
The narrow streets and alleyways of the Lebanese capital echoed with the strains of patriotic songs broadcast by radio and television stations.
People in shops and cafes were glued to their television sets tuned to stations carrying non-stop coverage of the events in the West Bank and Jerusalem.
All Arab leaders have rung Mr Arafat to extend their support and several have protested to Washington over Israel's Good Friday campaign.