Activists accused the military of massacring women and children in the worst violence in 11 months of unrest.
But the government denied the claims, saying activists were engaging in a propaganda campaign.
A draft UN resolution is still under discussion, with Russia indicating it is still not happy with the wording.
He said Moscow had tabled amendments to the text to try and ensure the UN would not appear to be taking sides in a civil war.
A vote had been expected to take place later, but Mr Lavrov said it would be a “scandal” to ask the council to vote on the resolution in its current form.
Russia is Syria’s main ally on the council, and has said it will veto any resolution calling on Mr Assad to stand down.
Moscow has continued to supply weapons to Syria despite the protests.
An activist in Homs told the BBC that it was the worst violence he had seen since anti-government protests began last March.
“It’s an awful situation. Two hours ago, three hours ago they started this shelling, we have no reason why,” he said.
The UK-based Syrian Observatory for Human Rights and the Syrian Local Coordination Committees both said the death toll had exceeded 200 after shelling began late on Friday.
The Syrian National Council, an umbrella group for Syria’s opposition factions, said 260 people had died and accused government forces of “randomly bombing residential areas”.
“The Syrian National Council calls on everyone around the world to speak up and do something to stop the bloodshed of innocent Syrians,” it said in a statement.
Homs was one of the first cities to join anti-Assad protests, and became one of the focal points of dissent after government forces fired on crowds in April last year. Many army defectors have sought refuge in the city.
Activists said most of the deaths were in the residential area of Khalidiya.
Reports said a hospital had been destroyed in Khalidiya, and residents said more than 30 houses had been wrecked in the barrage.
“We were sitting inside our house when we started hearing the shelling. We felt shells were falling on our heads,” Khalidiya resident Waleed told Reuters news agency.
Video footage emerged on the internet showing several bodies covered in blood with a voiceover saying the bombardment was still going on.
The BBC’s Jim Muir in Lebanon says a death toll higher than 200 would make it by quite a long way the bloodiest day since protests began.
State media dismissed the reports as a “hysterical campaign of incitement” by armed gangs designed to influence the UN.
“The civilians shown by satellite television stations are citizens who were kidnapped and killed by armed gunmen,” said a report on Sana news agency.
International media outlets are restricted in Syria, making it difficult to verify the claims of either side.
Meanwhile, activists have attacked Syrian embassies around the world.
About 20 protesters forced their way into the Syrian embassy in Berlin late on Friday and damaged offices, police said.
German TV showed a Syrian resistance flag hanging from one of the windows and graffiti sprayed on the outside of the building.
About 150 demonstrators also gathered outside the Syrian embassy in London early on Saturday and five people were arrested after entering the building.
In Cairo, protesters stormed the embassy building, smashing furniture and setting fire to parts of the building.
Syria has been gripped by nationwide protests against Mr Assad’s regime for almost a year.
The UN stopped estimating the death toll after it passed 5,400 in January, saying it was too difficult to confirm numbers.
The Syrian government says at least 2,000 members of its security forces have been killed fighting “armed gangs and terrorists”.