Syrian troops advanced on Monday into the rebel-held Khaldiyeh district of central Homs amid heavy shelling on the 10th day of an offensive, activists and an NGO said.
A watchdog also reported five people killed in two explosions -- one a suicide car bombing -- in a regime-held area of the city.
"The ruthless campaign against Homs is continuing for the 10th day in a row. Regime forces have been able to enter parts of Khaldiyeh after heavy shelling and scorched-earth tactics," activist Abu Bilal told AFP via Skype.
"The situation is similar to Qusayr," he said of the key town in Homs province which was recaptured by the army backed by Hezbollah fighters after a fierce campaign on June 5.
The activist said the assault was the fiercest in Homs since the beginning of the uprising against President Bashar al-Assad in March 2011.
He said the army was using "every kind of deadly weapon, from planes and rocket launchers to artillery, mortars and tanks".
Abu Bilal estimated the army controlled around 30 percent of the neighbourhood, which is north of central Homs, but the pro-regime Al-Watan newspaper said troops now controlled "most of Khaldiyeh".
"The Syrian Arab army brought most of the Khaldiyeh neighbourhood of Homs under its control," reported the daily, which is close to the government.
Both activists and the army said that regime forces had gained control of areas around the Khalid Bin Walid mosque in southern Khaldiyeh.
Videos filmed by activists showed massive destruction in the area, and the sound of heavy shelling.
Footage showed shells landing by the mosque's silver domes, sending up shocks of orange sparks and billowing white smoke.
The Syrian Observatory for Human Rights reported "violent clashes between rebel fighters and regime troops and gunmen on the outskirts of Khaldiyeh".
"There is a smell of death because many bodies are buried under the rubble of buildings, and the heat is making them rot faster," said another activist, Abu Rami.
"The army has also used explosives that give off a disgusting smell," he told AFP via the Internet.
The United Nations has estimated some 2,500 people are trapped amid the fighting that began 10 days ago.
The Observatory reported a suicide car bomb attack in the regime-held Akrameh district of Homs that killed five people, as well as a blast in the Nozha district.
"We know of at least one car bomb, though two shells hit the neighbourhood at the same time. At least five people were killed and 30 injured in the attack," said Observatory director Rami Abdel Rahman of the Akrameh attack.
"All those killed were civilians," he added.
Akrameh is home to a majority Alawite population, the religious community of which Assad is a member.
The Observatory could not verify what caused the blast in the Nozha area, also home to a majority Alawite community.
Monday's violence comes a day after at least 95 people were killed throughout Syria, the group said.