A Syrian government assault on the rebel bastion of Qusayr raged into a second day Monday, with at least 28 members of Lebanon's Shiite group Hezbollah reported killed as they fought alongside the army.
As official media reported that the army was consolidating its grip on Qusayr, a strategic prize in the two-year conflict, the ruler of Qatar, which backs the rebellion, slammed international inaction on Syria.
The battle began on Sunday, when government troops backed by Hezbollah stormed the western town, casting a shadow over US-Russian efforts to organise a peace conference on Syria.
The Syrian Observatory for Human Rights said the fighting had left at least 56 rebels dead, six of them on Monday, and four civilians including one woman.
Quoting "reliable sources", it said that "28 members of Hezbollah's elite forces were killed and more than 70 others wounded in clashes in the town of Qusayr yesterday," Sunday.
"The death toll is expected to rise because three of the wounded are in serious condition."
A source close Hezbollah told AFP at least 20 members had been killed in Syria, and around 30 more wounded.
The official SANA news agency reported on Monday that Syrian troops "are restoring order and security to the eastern part of Qusayr, eliminating terrorists (the regime term for rebels), destroying their dens and defusing bombs near the centre of the town".
State television said troops were also hunting down insurgents in the western and eastern parts of Qusayr.
The assault began early Sunday as warplanes raided Qusayr which was also pounded with heavy artillery to pave the way for a ground offensive.
"We struck from several fronts -- south, east and northeast," one soldier told state television from the rebel bastion as troops reportedly recaptured the town hall.
Activist denied they had advanced that far, although one of them told AFP the assault was one of the fiercest since the uprising against the regime of President Bashar al-Assad erupted in March 2011.
"Yesterday was the most violent, most difficult day in the whole of the Syrian revolution," activist Hadi al-Abdullah told AFP.
"I've never seen so much shelling... Qusayr was being shelled from all sides."
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The town is considered strategically important because it sits between Damascus and the coast and is near the Lebanese border.
"If the army manages to take control of Qusayr, the whole province of Homs will fall," said Observatory director Rami Abdel Rahman.
The regime has made recapturing Qusayr and nearby rebel areas of Homs province a key objective, and fighting has raged in the region for months.
In Doha, the Qatari emir, Sheikh Hamad bin Khalifa al-Thani, criticised the international community, saying it had failed to end the bloodshed in Syria.
"It is no longer acceptable that influential states in the international community do not act to end the horrific tragedy and escalating humanitarian catastrophe," Sheikh Hamad said.
He also lamented the "failure of all international and Arab initiatives to get the Syrian regime to listen to the sound of reason".
His remarks came amid mounting condemnation of the assault on Qusayr.
Syria's umbrella opposition National Coalition, warning that "a civilian massacre will soon take place" has urged the Arab League to convene an emergency meeting of Arab foreign ministers and take measures "to protect Qusayr".
UAE Foreign Minister Sheikh Abdullah bin Zayed al-Nahayan called for "the repressive machine in Damascus" to be stopped, while the French foreign ministry urged "all the players in a position to avoid a new massacre of the Syrian civilian population to mobilise without delay".
Foreign ministers of the so-called Friends of Syria group of nations are due to meet on Wednesday in Jordan, ahead of a planned Syria peace conference which Washington and Russia are hoping to organise.
Branches of the divided opposition met in Madrid on Monday seeking to harmonise their approach, their Spanish government hosts said.
On the humanitarian front, aid organisation Oxfam warned that as the hot Middle East summer approaches health risks could increase for hundreds of thousands of Syrian refugees in Jordan and Lebanon.
The UN says that more than 1.5 million Syrians have fled the conflict and estimates that more than 70,000 people have been killed since March 2011.
The Observatory has a higher toll of more than 94,000 killed.