Syria's military pounded rebel bastions in Damascus on Tuesday and Saudi Arabia demanded an arms embargo on what it called President Bashar Assad's genocidal and illegitimate regime.

Attacking Iran, Russia and Lebanon's Hezbollah for supporting Assad, Saudi Foreign Minister Prince Saud al-Faisal said the kingdom could not be silent and called for arms to be supplied to Syrian rebels, now militarily on the back foot.

"Syria is facing a double-edged attack, it is facing genocide by the government and an invasion from outside the government, and ... a massive flow of weapons to aid and abet that invasion and that genocide. This must end," he told a news conference with U.S. Secretary of State John Kerry in Jeddah.

"The kingdom calls for issuing an unequivocal international resolution to halt the provision of arms to the Syrian regime and states the illegitimacy of the regime," Prince Saud said.

In Damascus, Assad's gunners fired mortars and artillery at Zamalka and Irbin, just east of the government-held city center, in an assault backed by air strikes, opposition activists said.

Mostly Sunni Muslim rebels who grabbed footholds in Damascus nearly a year ago now say they face a grinding advance by the Syrian military, buoyed by support from Assad's regional Shi'ite allies, notably Iranian-backed Hezbollah fighters on the ground.

If the insurgents are driven from the capital's eastern suburbs, they would lose arms supply routes and suffer a severe blow in their drive to end four decades of Assad family rule.

The Saudi minister's strongly worded remarks reinforced signs that the Syrian war is entangling much of the Middle East.

Security in neighboring Iraq and Lebanon, where the conflict has aggravated Sunni-Shi'ite tensions, has crumbled.

Suicide bombers killed eight people north of Baghdad on Tuesday, a day after 39 people died when 10 car bombs exploded in the capital. Violence has spiraled in Iraq since April.

Getting out of hand

In Lebanon, clashes between the Lebanese army and gunmen led by a fiercely anti-Hezbollah Sunni cleric engulfed the southern port of Sidon on Sunday. At least 40 people were killed, including 18 soldiers, security sources said.

Sectarian hatred has even flared in Sunni-majority Egypt, where a crowd attacked and killed five Shi'ites on Sunday.

Lakhdar Brahimi, the U.N.-Arab League mediator, urged the United States and Russia to help "contain this situation that is getting out of hand, not only in Syria but also in the region".

Speaking in Geneva before preparatory talks with U.S. and Russian officials, he said he doubted that a Syria peace conference proposed by Moscow and Washington could take place next month, citing disarray among Assad's political opponents.

More than 93,000 people have been killed in Syria since peaceful protests erupted in March 2011. Assad's violent response helped generate what is now a civil war that has driven nearly 1.7 million refugees into neighboring countries.

Outgunned rebels are looking to Western and Arab nations to help them to reverse Assad's battlefield gains of the last few weeks. But although the United States announced unspecified military aid this month, it is unclear whether this can shift the balance against the Syrian leader and his allies.

Kerry wants to ensure that aid to the rebels is properly coordinated, in part out of concern that weapons could end up in the hands of Islamist militants who are prominent in their ranks.

"Our goal is very clear, we cannot let this be a wider war, we cannot let this contribute to more bloodshed and prolongation of the agony of the people of Syria," he said.

Saudi Arabia, a Sunni state which views Shi'ite Iran as its arch-rival, has increased aid to Syrian rebels in recent months, supplying anti-aircraft missiles among other weapons.

Prince Saud denounced foreign involvement in Syria "by Hezbollah and other militias supported by the forces of the Iranian Revolutionary Guard", and also took a swipe at Moscow.

"There is no logic that allows Russia to publicly arm the Syrian regime and the foreign forces that support it."

Also on Thursday, a Syrian branch of Al-Qaida on claimed responsibility for what the group said were suicide attacks on security compounds in Damascus that killed at least five people, while troops fought rebels on the edge of the capital in the latest surge of violence in the Syrian capital.

The claim by Jabhat al-Nusra — the first in months — came as the UN's special representative trying to end Syria's civil war said hopes for convening a peace conference next month are fading.

The Nusra Front has emerged as the most effective fighting force on the side of the opposition fighting to oust President Bashar Assad. The group has previously claimed car bombings and attacks on government soldiers and its fighters have been leading other rebels groups in battles for military bases in the north much of which is under control of the opposition.

The group's affiliation with Al-Qaida, however, has significantly contributed to the reluctance of the opposition's Western backers to arm the rebels with heavier weapons.

More than 93,000 people have been killed since the Syrian conflict began in March 2011. It started as peaceful protests against Assad's rule but turned into a civil war after some opposition members took up arms to fight the government's harsh crackdown on dissent. Since then, radical groups like the Nusra front have gained influence on the battlefield as opposition's political leadership struggles to unify its ranks.

The conflict has taken increasingly sectarian tones with Sunni Muslims dominating rebel groups fighting against Assad's regime, which is predominantly Alawite, an offshoot sect of Shiite Islam.

Even the most modest international efforts to end the Syrian conflict have failed.

In Switzerland, UN's special envoy to Syria, Lakhdar Brahimi, told reporters he still hopes a second round of international negotiations to find a political solution to the conflict can be convened in Geneva — but not until later in the summer.

"Frankly now, I doubt whether the conference will take place in July," he said, noting that the Syrian opposition is not meeting until early July and probably would not be ready.

"Since our previous meeting here on the 5th of June, the situation on the ground in Syria has hardly improved. It is still relentless destruction, killing, more suffering, more injustice, and more uncertainty for the future of the Syrian people," Brahimi said.

Brahimi was mediating a meeting between the U.S. and Russia, which are at loggerheads over the conflict.

Russia supports the regime and Washington has backed the opposition, which insists Assad should relinquish power before any talks with Damascus can take place. Assad has repeatedly dismissed demands to leave power and said he has the right to run for another term in next year's presidential elections.

Jabhat al-Nusra claimed responsibility for Sunday's attacks in Damascus in a statement posted on a militant website, warning Assad that his "criminal regime" should know that its fighters "do not fear any confrontation with the enemies."

The group said it had sent seven suicide bombers wearing Syrian military uniforms to break into a police station in northern Damascus and a security compound in a southern district of the capital. The group also posted several pictures claiming to show the attackers. Their faces blurred, the men are seen wearing military uniforms and holding Kalashnikovs as they sit on the ground with Jabhat Al-Nusra black banner hanged behind them.

"The criminal and traitor regime should know that Sunni people stand on solid ground and brave men who do not fear any confrontation with the enemies...and they are ready to sacrifice their blood in order to protect the souls and honor of their people," the statement said.