BEIRUT (AP) — Syria’s military sent tanks and other reinforcements toward the restive central city of Homs on Monday, in what appears to be preparations by President Bashar Assad’s regime for an offensive aimed at retaking rebel-held neighborhoods, activists said.

Syria-based activist Mustafa Osso told The Associated Press he does not think the regime will be able to retake Homs through military force as residents plan to fight until “the last person.” He added that Homs is facing “savage shelling that does not differentiate between military or civilians targets.”

Rami Abdul-Rahman, who heads the Britain-based activist group Syrian Observatory for Human Rights, said he expects the regime to try retake the Baba Amr district of Homs. Many Syrians call Baba Amr “Syria’s Misrata,” a reference to the Libyan city where rebels fought off a brutal government siege for weeks, managed to hold the city and went on to play a key role in overthrowing dictator Moammar Gadhafi last year.

“The human loss is going to be huge if they retake Baba Amr,” Abdul-Rahman said.

The Observatory said that Monday’s shelling of Baba Amr killed five civilians.

In neighboring Lebanon, security officials said at least three wounded Syrians were brought for treatment in the eastern town of Chtoura. The officials, who spoke on condition of anonymity in line with regulations, said the wounded came from the Baba Amr attacks.

Amateur videos posted online showed what activists said were shells falling into Baba Amr. Black smoke billowed from residential areas.

Clashes between military rebels and Syrian forces are growing more frequent and the defectors have managed to take control of small pieces of territory in the north as well as parts of Homs province, which is Syria’s largest stretching from the border with Lebanon in the west to Iraq and Jordan in the east. Increasingly, Syria appears to be careening toward an all-out civil war.

Funeral of two protesters in Damascus on Sunday. (photo credit: AP)

Funeral of two protesters in Damascus on Sunday. (photo credit: AP)

Assad’s authoritarian regime may be trying to subdue Homs — an important stronghold for anti-Assad groups — before a planned referendum Sunday on a new constitution. The charter would allow a bigger role for political opposition to challenge Assad’s Baath Party, which has controlled Syria since a 1963 coup.

But the leaders of the 11-month-old uprising against Assad have dismissed the referendum as an attempt at superficial reforms that do nothing to crack the regime’s hold on power. Assad still counts on support from Iran and allies such as Russia, which fears losing its main Arab partner. But his government is facing escalating pressure and isolation from Western and Arab states.

In Kabul, two senior members of the U.S. Senate Armed Services Committee urged international cooperation to help supply the anti-Assad rebels with weapons and other aid. Both Arizona Sen. John McCain and Sen. Lindsey Graham of South Carolina, however, stopped short of endorsing direct U.S. military involvement.

“The United States doesn’t have to directly ship weapons to the opposition, but there are a whole lot of things that can be done” through groups such as the Arab League, McCain told reporters.

Graham said it was “shameful” for the U.S. not to have a prominent role to help the rebel forces, saying that breaking Syria’s ties to Iran “could be as beneficial to our efforts to contain a nuclear armed Iran as sanctions.”

“If the Syrian regime is replaced with another form of government that doesn’t tie its future to the Iranians, the world is a better place,” he said.

Osso said the three convoys heading toward Homs comprise dozens of vehicles from the eastern suburbs of the capital Damascus, an area that was reclaimed by Assad troops from rebels late last month.

In embattled Homs, rebel-held neighborhoods such as Baba Amr and Khaldiyeh have been under government attack since Feb. 4. Phone lines and Internet connections have been cut with the city, making it difficult to get firsthand accounts from Homs residents.

The U.N. last gave a death toll for the conflict in January, saying 5,400 had been killed in 2011 alone. But hundreds more have been killed since, according to activist groups. The group Local Coordination Committees says more than 7,300 have been killed since March of last year. There is no way to independently verify the numbers, however, as Syria bans almost all foreign journalists and human rights organizations.

The Observatory said that troops conducted raids Monday in the southern village of Harrah where at least nine people were detained.

On Sunday, activists said at least 18 people were killed in Syria, including a senior state prosecutor and a judge who were shot dead by gunmen in the restive northwestern province of Idlib.

Copyright 2012 The Associated Press.