The mobilization around the resistance stronghold in central Syria was an ominous sign that President Bashar al-Assad's regime was preparing a ground assault after weeks of shelling the district of Baba Amr, which the opposition has dubbed "Syria's Misrata" after the Libyan city where rebels fought off a government siege.

Syrian-based activist Mustafa Osso said Assad's military should be ready to face stiff battles as residents planned to fight until "the last person". He said Homs was facing "savage shelling that does not differentiate between military or civilians targets".

"The human loss is going to be huge if they retake Baba Amr," said Rami Abdul-Rahman, who heads the British-based activist group Syrian Observatory for Human Rights. The group said at least eight people were killed by shelling in parts of Homs on Monday.

Amateur videos posted online showed what activists said were shells falling on Baba Amr with black smoke billowing from residential areas. Phone lines and internet connections have been cut to the city, making it difficult to get firsthand accounts from residents.