More than 70 people died in one of the bloodiest days of the eight-month Syrian uprising, activists said on Tuesday, as the growing isolation of President Bashar al-Assad's regime drew an increasingly angry reaction from his loyalists.

More than 100 of his supporters stormed the Jordanian embassy in Damascus overnight -- the fourth regional mission to be targeted since the Arab League voted on Saturday to impose sanctions -- after Jordan's King Abdullah II became the first Arab leader to publicly call for Assad to quit.

Buoyed by the fast-growing diplomatic pressure, the Syrian opposition stepped up its contacts with the regime's remaining bulwarks, holding talks in Moscow, which last month joined Beijing in vetoing a UN Security Council resolution that would have threatened "targeted measures."

Neighbouring Turkey, a former close Syrian ally that has been one of the most outspoken champions of reform, prepared to hold talks in Morocco with Arab leaders Wednesday that were expected to be dominated by the bloodshed.

In a sign of the potential for civil war in one of the Middle East's most pivotal countries, five regular army troops were killed on Tuesday in clashes with mutinous soldiers who refused orders to shoot on civilians, a human rights group said, after 34 were killed the previous day.

The fighting erupted in the town of Hara in Daraa province, where the unprecedented protests against Assad's 11-year reign erupted in March, the Syrian Observatory for Human Rights said.

In Idlib province in the northwest, close to the Turkish border, "clashes between the regular army and armed men, probably deserters, caused at least 14 casualties -- dead and wounded, the Britain-based watchdog added.

Desertions within Assad's security forces -- which have a professional hard core but also much larger conscripted ranks -- triggered much of Monday's death toll of more than 70.

A total of 34 soldiers and 12 suspected army deserters were killed in clashes, as well as 27 civilians shot dead by security forces in the regime's intensifying crackdown, the Observatory said.

Most of the victims were killed in Daraa province, the uprising's birthplace close to the border with Jordan, which has become increasingly outspoken about the bloodshed in its northern neighbour.

King Abdullah II on Monday became the first Arab leader to openly call for Assad to step down, two days after the Arab League took the rare move of suspending Syrian membership of the 22-nation bloc and imposing sanctions.

"I believe, if I were in his shoes, I would step down," the king said in a BBC interview. "I would step down and make sure whoever comes behind me has the ability to change the status quo that we're seeing."

Angry Assad loyalists stormed the Jordanian embassy in Amman on Monday evening in response, mirroring similar attacks on the Qatari, Saudi and Turkish embassies, the ambassador told the Jordanian press.

"Nearly 120 people protested in front of the Jordanian embassy in Damascus on Monday evening and two of them managed to break into the outside courtyard of the embassy and tear down the Jordanian flag," ambassador Omar al-Amad told the Al-Dustur and Al-Ghad newspapers.

"Syrian security forces did not intervene to prevent the incursion into the embassy compound by these two individuals," he added.

Jordan and other Arab governments are due to hold talks in Morocco on Wednesday with Turkey whose Foreign Minister Ahmet Davutoglu has warned that Middle East leaders who cannot meet the demands of their people "will go".

"Those in the Middle East who are not at peace with their people and cannot satisfy them will go," Davutoglu told a parliamentary committee on Monday, adding that Turkey will "take a very firm stand."

Ankara's tough stance has won it the growing adulation of anti-government protesters in Syria. Hundreds of demonstrators took to the streets of the main northern city of Aleppo late on Monday, waving Turkish flags and chanting: "Thank you, Turkish government," Turkey's NTV television channel reported.

Ahead of the Rabat meeting, Arab League chief Nabil al-Arabi was to hold talks with the Syrian opposition later on Tuesday in a bid to broker a unified vision of a post-Assad era.

The Syrian opposition was also holding talks with Russia -- one of the regime's rapidly dwindling band of allies -- in a bid to intensify the pressure on Assad to step aside.

"We want the crisis to be overcome," Burhan Ghalioun, the Paris-based leader of the opposition Syrian National Council told the ITAR-Tass news agency ahead of his meeting with Foreign Minister Sergei Lavrov.

"And we would like this without military interference from the outside," he added, alluding to Moscow's fears of a repetition of the UN-mandated NATO-led military intervention in Libya that led to the overthrow of Moamer Kadhafi's regime, another Soviet-era ally of Russia.