- NEW: At least four died in Syria on Sunday, opposition activists say
- A bomb is launched every 10 minutes, an opposition group says
- The U.N Security Council members approve a resolution to allow observers into Syria
- A U.N. monitoring team will be dispatched "as soon as possible," Ban Ki-moon says
(CNN) -- Government helicopters pounded the besieged city of Homs from the sky, opposition activists said Sunday, three days after a so-called cease-fire in Syria.
In addition, "one bomb is being shelled every 10 minutes from the military academy, aiming at al-Wair neighborhood in Homs," said the Local Coordination Committees of Syria, a network of opposition activists.
At least two people were killed Sunday in Homs, said the Syrian Network for Human Rights, another opposition group. Two others died in Aleppo on Sunday, a day after they were injured when regime forces opened fire at a funeral procession, the group said.
Across the country, security forces also stormed the city of Buqros, in the eastern Deir Ezzor province, and carried out a wave of random arrests, the LCC said.
The latest reports of violence came three days after a deadline to stop the bloodshed and one day after the U.N. Security Council voted unanimously to authorize unarmed observers to travel to Syria to monitor the shaky cease-fire.
The team will be dispatched "as soon as possible," U.N. Secretary-General Ban Ki-moon said Saturday.
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 quell the bloodshed.
Still, the resolution marks the Security Council's first on Syria since the conflict gripping the country broke out more than a year ago.
Though critics called the move underwhelming, the U.N. ambassador from Russia -- 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.
Homs, Syria, under a shaky cease-fire 
Deaths amid fragile Syria cease-fire 
Protests test Syria's cease-fire 
Blair: No confidence in what Syria says "There have been too many casualties, too much suffering to befall the Syrian people," Ambassador Vitaly Churkin said.
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 -- which both have major trade ties with Syria -- had blocked Security Council attempts to pass resolutions condemning the government of President Bashar 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.
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.
Renewed shelling on Homs on Saturday "absolutely" constituted 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.
While the council's decision "does not satisfy us fully," Syria "will be on board" with the resolution, Syria's U.N. ambassador Bashar Jaafari said.
Jaafari also called for a lifting of sanctions, blaming them for costing his country "billions of dollars."
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."
Separately, Iran's chief nuclear negotiator Saeed Jalili told reporters in Turkey that the Syrian issue "has only one solution, and that is democracy."
But the LCC said government forces targeting opposition neighborhoods in Syria killed 20 people on Saturday.
The dead included a citizen journalist who was filming tanks shelling a Homs neighborhood when he was killed, the LCC said. The cameraman, Salim Shalab Al-Sham, was 26 years old, the group said.
State-run media also reported clashes, describing them as encounters between security forces and "armed terrorists." The Syrian Arab News Agency said a citizen was "martyred" and 12 others injured when shelling struck residential areas in al-Zahra, a predominately Alawite, pro-Assad neighborhood in Homs province.
The Syrian regime has consistently blamed the violence in the country on "armed terrorist groups," but many world leaders have said the government is lethally cracking down on dissidents seeking true democracy and an ouster of al-Assad, whose family has ruled Syria for 42 years.
CNN cannot independently verify reports of violence and deaths as the government has severely restricted access by international media.
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.
CNN's Saad Abedine, Richard Roth, Salma Abdelaziz, Amir Ahmed, Elise Labott and Arkady Irshenko contributed to this report.
