The team will be dispatched "as soon as possible," U.N. Secretary-General Ban Ki-moon said.
The 15-member council approved the deployment of an advance team of 30 monitors meant to pave the way for a larger group of up to 250 observers, calling on Syria to provide them unimpeded freedom of movement.
That second deployment, however, first rests on how the cease-fire holds and whether discussions between Syria and U.N.-Arab League envoy Kofi Annan can make headway to stem the bloodshed.
Still, the resolution marks the United Nations' first on Syria since the conflict gripping the country broke out more than a year ago. The resolution is thought to add new pressure to the government of President Bashar al-Assad, already confronted with the debilitating effects of economic sanctions.
Though critics called the move underwhelming, Russia's ambassador to the U.N., whose country has previously blocked the council's resolutions, reminded those strident for action in Syria that the text requires all sides to put down their weapons.
"There have been too many casualties, too much suffering to befall the Syrian people," Ambassador Vitaly Churkin said.
He warned that the unrest could affect regional peace and stability, and said the timing of the council's decision comes at an "extremely critical juncture."
Churkin noted that Russian support of the resolution came despite a perceived lack of dialogue about the future political process in Syria, "something which unfortunately is missing."
He also said that his government has been discouraged by a lack of objective information and has called on Syria to allow in international journalists.
Until Saturday, Russia and China had blocked Security Council attempts to pass resolutions condemning the government of al-Assad. While the two countries have said they want an end to the violence, both have argued that previous resolutions were not even-handed.
U.S. Ambassador to the U.N. Susan Rice welcomed Saturday's long-awaited resolution, but said the United States was "under no illusions" about its immediate effect. She called the deployment "an important test of the Syrian government's intentions," before a broader observer mission can develop.
Rice, the current Security Council president, pointed to reports of ongoing violence, which are already "raising renewed doubts about the sincerity" of Syrian authorities to end hostilities.
The country's renewed shelling of the city of Homs on Saturday "absolutely" constitutes a violation of the current cease-fire, she said.
Still, Ban said he "will make sure that this advanced observer mission will be dispatched as soon as possible." Ban further pledged to try to develop by Wednesday a more concrete proposal for an official, and likely more broadly defined, observer mission.
Syria's U.N. ambassador responded Saturday by saying "the ball now is in the camp of those supporting the armed groups in Syria," a reference to a long-held position that regional players are seeking to destabilize Syria by fomenting an insurrection within its borders.
"Double standards and double language will not be sufficient to prove the credibility of those who are manipulating the armed groups, supporting them, hosting them, training them and pushing them towards committing further violence in Syria," Ambassador Bashar Jaafari said.
The Syrian ambassador also called for a lifting of sanctions, blaming them for costing his country "billions of dollars."
And yet, while the council's decision "does not satisfy us fully," Syria "will be on board" with the resolution, Jaafari said.
Earlier, Ambassador Mark Lyall Grant of the United Kingdom warned that a narrow window now exists to improve conditions on the ground.
The U.K., he said, welcomes the resolution, but regrets "that it comes only after the Syrian people have for over one year suffered unimaginable brutality at the hands of a regime that has prioritized its own survival over the needs, rights and aspirations of the people it should serve and protect."
Peter Wittig, the German ambassador to the U.N., added that it's come "deplorably late, but hopefully not too late."
"We must remain vigilant," he noted. "Too many commitments made by Damascus in the past have not been kept. We must not tolerate further brinkmanship."
During a separate press conference in Istanbul, Turkey, Iran's chief nuclear negotiator Saeed Jalili told reporters that the Syria issue "has only one solution, and that is democracy."
"The people of Syria should take part in a free election in Syria and decide for themselves," he said through a translator. "We believe that any foreign interference, any triggering of violence, are not going to resolve the problems in Syria."
Meanwhile, activists inside the embattled country reported Saturday that government forces again targeted opposition neighborhoods. The apparent actions occurred despite a tenuous cease-fire in place since Thursday, as part of a 6-point peace plan laid out by the special envoy.
In escalating attacks, at least 20 people were killed by security forces, said the Local Coordination Committees (LCC) of Syria, a network of opposition activists. State media also reported the clashes, describing them as encounters between security forces and "armed terrorists."
Other demands of the Annan plan include the release of detainees, allowing access for humanitarian aid and international media, and the withdrawal of troops and heavy weapons from residential areas.
Syria, however, has not been in full compliance with the plan, and troops and heavy weapons remain in population centers despite an agreement to withdraw, Rice said.
At least 11 people were killed Saturday in the flashpoint city of Homs, where the Syrian army resumed mortar shelling in several neighborhoods, according to opposition groups.
Abu Abdel Rahman, a spokesman for Sham News Network, described how a cameraman on his way to film the shelling was among those killed in the city.
Five more people were killed in the western city of Aleppo, three of them as government forces opened fire on mourners during a funeral, the LCC said.
Amateur video, apparently posted online Saturday, showed people running amid sounds of heavy gunfire. CNN cannot confirm the video's authenticity.
Syrian state TV later reported that security forces had clashed with armed terrorist groups in Aleppo, who allegedly were taking aim at civilians. SANA, the state-run news agency, said two law enforcement officers were killed and an army colonel kidnapped in separate attacks by the alleged terrorists. Syria has consistently pointed to "armed terrorists" as a primary cause for the unrest.
In Daraa, government troops opened fire on protesters, injuring at least 20, according to the Syrian Observatory for Human Rights, a London-based opposition group. Regime forces arrested five people after raids on their homes, the group reported.
Opposition groups and journalists also described heavy gunfire Saturday near a refugee camp along the Syria-Turkey border.
The attacks come one day after protesters poured onto Syria's streets, seemingly testing whether al-Assad would stick to a provision in Annan's plan that allows for peaceful demonstrations.
But the envoy's spokesman, Ahmad Fawzi, said Friday that there was still a long way still to go.
"We are worried about the operational deployment of heavy armor in population centers," he said. "They do not belong there. And we are working with the government and with the opposition for a full cessation of violence in all its forms."
Anti-government protests erupted in March last year, followed by a bloody government crackdown on civilians and opposition groups, which have sprung up in various cities across the country.
The United Nations estimates at least 9,000 people have died since the protests began, while others put the death toll at more than 11,000.
