A top defector from the Syrian military is urging armed rebel groups to align and follow the leadership of the Free Syrian Army.

Uniting all efforts will strengthen the anti-government movement and safeguard the nation, Brig. Gen. Mustafa Sheikh said in a video posted on YouTube on Saturday.

Sheikh was the first brigadier general to announce his defection from President Bashar al-Assad's forces. He was accompanied in the video by Free Syrian Army commander Col. Riad al-Assad.

The move addressed a key concern for observers of the Syrian crisis both inside and outside the country - that armed rebel groups were disjointed and divided.

"The division is over. All the parties involved in the revolution carried out all the efforts to form one united front to better represent and defend the Syrian people," Free Syrian Army Lt. Riad Ahmed said. "In the past, there were some minor technical disagreements, but this is all behind us from now on."

A Syrian rebel leader vehemently refuted the government's claim that so-called "terrorists" - not the regime itself - launched a series of explosions in Damascus that killed dozens.

"This is the regime's game. This is how they play their dirty tricks. They carry out these types of explosions from time to time to get more international support and compassion," Capt. Ammar al-Wawi of the rebel Syrian Free Army said Sunday. "They are desperately trying to prove to the world that they are fighting against armed gangs, but the reality is they are the ones who are doing all the killings."

Two explosions rocked parts of Damascus on Saturday, including Syrian government facilities, state-run media reported.

The Syrian Arab News Agency said 27 people were killed after two "booby-trapped" cars exploded in crowded areas in the capital. The blasts also injured 140 people and caused serious damage to surrounding buildings, SANA said.

After laying out plans aimed at halting the bloodshed in Syria, Kofi Annan, the special U.N. envoy to the country, will meet again with President Bashar al-Assad on Sunday in hopes of getting answers to his proposals.

In what he described as a candid and comprehensive discussion, Annan met with al-Assad on Saturday about a cease-fire, the release of detainees and allowing unfettered access to agencies like the Red Cross to deliver much needed aid, a U.N. statement said.

But while Annan waited for answers in Damascus, fresh violence erupted once again in cities across the country.

Clashes broke out between the Syrian army and rebel fighters in the Damascus suburbs and Aleppo, said the Local Coordination Committees of Syria, a network of opposition activists.

And in a phone call with a Binish town elder, a major general in al-Assad's military demanded the people of Binish hand over weapons used by defected soldiers and the rebel Free Syrian Army within 24 hours - or the town will be bombed and stormed early Monday morning, according to the Binish Coordination Committee, part of the LCC.

A former United Nations secretary-general met with Syria's president Saturday in the latest diplomatic attempt to halt the bloodshed in the country.

But on the same morning, at least 15 people died from fresh violence across Syria, opposition activists said.

Kofi Annan, the joint special envoy to Syria for the United Nations and the Arab League, met President Bashar al-Assad in Damascus "to seek an urgent end to ... human rights violations and to initiate efforts to promote a peaceful solution" to the violence that has wracked the country for nearly a year, his spokesman said.

Time is running out for a diplomatic way of ending the crisis, said Haytham Manna of the opposition Coordinating Committee of Democratic Transition in Syria.

"We are at the last moments of reaching a political solution. We are getting to the point of no return," said Manna, a Paris-based dissident. "If we can't reach a political agreement today, we will head toward the abyss. ... The regime is pushing the country as a whole toward a full scale armed struggle between the very well organized military institution and our people."

While carnage mounts in the streets of Syria, the war of words rages on as well.

"We are not happy to see brothers killing each other," Syrian Foreign Minister Walid Moallem said, insisting that no regime cares more about the Syrian people than his government.

The foreign minister told reporters no one is dying in Syria because of hunger or sickness, and said that despite an "economic international boycott," his government is providing all necessary services.

His words fly in the face of opposition activists and world leaders who say the regime's sustained slaughter has killed thousands.

In what the government touts as a move toward reform, Syria's constitutional referendum kicked off Sunday to widespread skepticism that the regime would stop slaughtering civilians.

The referendum on a draft constitution began in polling centers across the country Sunday morning, Syrian state-run TV reported.

But the unabated violence on the ground indicated nothing has changed in the nearly year-long onslaught by government forces.

At least 100 people were killed on the eve of the vote, almost half of them in Homs, according to the Local Coordination Committees of Syria, a network of opposition activists.

And on Sunday morning, rockets fell once again on the besieged Baba Amr neighborhood of Homs, said the Syrian Observatory for Human Rights, another opposition activist group

Syrian President Bashar al-Assad's forces pounded resistance strongholds Saturday, the opposition said, raising questions about what immediate effect a plan by world powers to end the violence will have in the hardest-hit areas.

At least 33 people were killed Saturday across Syria, according to the Local Coordination Committees of Syria, a network of opposition groups. Casualties included 17 people killed in the besieged city of Homs, the group said. The city at the center of resistance has endured more than three weeks of daily shelling.

Reports of renewed violence followed news Friday that dozens of countries agreed to increase pressure on al-Assad while laying groundwork for a political transition in Syria not unlike the international planning that preceded the fall of Libyan ruler Moammar Gadhafi last year.

A freelance cameraman who visited Homs recently put together a video that provides a rare glimpse of life in the embattled city and an even rarer close-up of the opposition movement in Syria.

At the headquarters of the government secret police, the cameraman - who uses the name Mani to avoid retribution by the government if he returns - finds himself in the thick of a battle. Some 200 members of the Free Syrian Army, made of military defectors, are involved in the attack. They explode a bomb below a rooftop position, where government snipers are trapped.

Mani's camera follows opposition fighters as they enter the government building, where room-to-room and stairwell-to-stairwell fighting ensues.

While aid workers struggle to access the most devastated parts of Syria, families in the ravaged city of Homs wonder when the misery inflicted by government forces will end.

Seven people - including a baby - died Tuesday from fresh shelling on three Homs neighborhoods, according to the Syrian Observatory for Human Rights, an opposition activist group.

"My husband died on the first day of the bombing. They didn't let me see his body; it was shredded to pieces. His blood is still in the streets," says Umm Khidir, one of several mothers holed up in a makeshift shelter after a weeks-long bombing campaign on the city.

She said her son is sick with a fever, but there's no medicine.

"He keeps crying and saying, 'I want daddy, I want daddy.' I can't bring his daddy back," she said, demanding to know why the world is not coming to their aid. "What is the world waiting for? For us to die of hunger and fear?"