Syrian tank forces killed at least 25 people in a thrust into the opposition hotbed of Homs aimed at stemming growing armed resistance to President Bashar al-Assad's crackdown on a seven-month-old popular uprising, residents said.
It was one of the highest daily death tolls in the large central Syrian city that has seen some of the most extensive protests in a tide of unrest where protesters are demanding an end to 41 years of repressive Assad family rule.
The clashes on Monday followed the deployment of loyalist militiamen in Sunni Muslim districts, fanning tension between the city's Sunni majority and members of Assad's minority Alawite sect, residents told Reuters by telephone.
Mindful of the threat of civil war in Syria, which straddles major fault lines of Middle East conflict, the Arab League offered on Sunday to host talks in Cairo between the opposition, who have formed a National Council, and the Damascus leadership.
But Syria's representative to the League said Syria had major reservations about the offer, while the opposition Syrian National Council said it could not engage in talks while Assad's military continued to storm restive cities and towns.
In Homs, 140 km (90 miles) north of Damascus, tanks firing heavy machineguns swept into Sunni districts of Bab Sbaa, Bab Dreib and Bab Amro where large protests demanding the removal of Assad have taken place regularly, residents and activists said.
They said loyalist forces encountered rudimentary resistance, although army deserters were helping some inhabitants defend their neighbourhoods and managed to hit several tanks with rocket-propelled grenades (RPGs).
"Most residents of Bab Sbaa have fled. The troops are firing heavily from tanks and from the roadblocks in the area. The fire coming from the other direction is small and intermittent," a local resident said by phone.
"Roadblocks have cut off every neighborhood from another, and random firing by troops manning them is common," said another resident, who gave her name as Manal.
Homs, the hometown of Assad's wife Asma, lies amid fertile farmland on the main highway to Aleppo, Syria's second city.
Homs is close to the border with Lebanon, which has begun to serve as a supply line to insurgents in the city and its countryside, including army defectors who have increased in numbers since the crackdown intensified two months ago.
Inspired by "Arab Spring" popular uprisings that have overthrown entrenched autocrats in Tunisia, Egypt and Libya, protests have spread across much of Syria calling for the Assad family's ouster and more political freedoms.
Syrian authorities blame the unrest on "armed terrorist groups" which they say have killed 1,100 army and police and are operating in Homs, killing civilians and prominent figures.
In Cairo, Arab League foreign ministers urged Syria's rulers and opposition to negotiate and decided to create a committee to work for a halt to the bloodshed. They stopped short of adopting a proposal to suspend Syria from the pan-Arab group.
Youssef Ahmad, Syria's representative to the Arab League, said its decision was "not transparent" and that Damascus could not accept taking part in any talks outside Syria.
Arab states were silent for months while Assad's troops tried to stamp out unrest with tanks and machineguns, but began to criticise Assad after the United States and European powers said he must go and slapped economic sanctions on Damascus.