SEOUL - UN Secretary General Ban Ki-moon on Monday voiced bitter frustration at the failure of the Syria ceasefire and stressed the need for international unity to end the violence.

"I am deeply disappointed that the parties failed to respect the call to suspend fighting," Ban said in the South Korean capital Seoul, where he received a peace prize from his home country.

"This crisis cannot be solved with more weapons and bloodshed," Ban said, calling on the UN Security Council, regional countries and all parties "to live up to their obligations and promote a ceasefire".

The four-day truce proposed by UN-Arab League envoy LakhdarBrahimi collapsed amid clashes, shelling and car bombings hours after it had been due to take effect with the start of Eidul Azha holidays on Friday morning.

The Syrian army and opposition forces blamed each other for breaking the ceasefire.

Although Ban did not seek to apportion blame in his speech, he noted the bombings of "densely populated" cities by the Assad regime.

The conflict, which began as an anti-regime uprising, is now a civil war pitting mainly Sunni rebels against President Bashar Assad's regime dominated by his minority Alawite sect, an offshoot of Shiite Islam.

Brahimi is expected to go to the Security Council in November with new proposals for talks between Assad and the opposition.

Russia and China have three times used their powers as permanent Security Council members to block resolutions that could have led to Syria sanctions. As long as the international community "remains at odds", the suffering of the Syrian people will only deepen, Ban said in Seoul. Brahimi, who is in Moscow to find a solution, has said that Syria's conflict is going from bad to worse.

"I have said and it bears repeating again and again that the Syrian crisis is very very dangerous, the situation is bad and getting worse," Brahimi said after talks with Russian Foreign Minister Sergei Lavrov.

Brahimi said that some bomb blasts "during the Eid period in the civilian population area are definitely terrorist acts by groups we have no contact with," calling them "definitely condemnable". The envoy called on the international community to come together and help the people of Syria. Lavrov said that Moscow was also "disappointed" that the truce plan was not heard by the opposing sides. "They are fighting more and more in Syria, provocations and inadequate responses to them are daily occurrences," Lavrov said.

He stressed Russia's position that the crisis will be resolved once Western powers and regional players like Turkey start negotiating with Assad, not just the opposition.

Moscow has repeatedly criticised Western powers for what it says are obstructions of peace efforts in Syria and last week alleged that the United States was coordinating arms deliveries to the rebels.

Meanwhile, explosions shook Damascus on Monday as warplanes launched their heaviest air raids yet and a car bomb struck.

The air raid blasts, heard coming from several outlying districts, rattled windows in the centre of the capital and were among the most intense in Damascus since the beginning of Syria's 19-month conflict. They were followed by a car bombing that state television said killed at least 10 people in the predominantly Christian and Druze area of Jaramana, just outside Damascus. A watchdog said 12 people had died and 15 been wounded.