Arab league Syria
Supporters of Syrian President Bashar al-Assad attend a rally in support of the army in Damascus. The president has denied responsibility for the crackdown against anti-government protesters, in which at least 5,000 people are estimated to have been killed. (Reuters)

The head of the Arab League's monitoring mission in Syria has angered protesters by saying he saw "nothing frightening" in the flashpoint city of Homs.

Sudan's General Mustafa Dabi said his team of observers were not overly concerned about the situation in the city, which has become a hotspot of unrest and the focal point of anti-government protests since March.

"There were some places where the situation was not good," Dabi said.

"But there wasn't anything frightening, at least while we were there. Things were calm and there were no clashes," he said.

His team found the situation "reassuring so far", he added.

"This was only the first day and it will need investigation. We have 20 people who will be there for a long time."

Activists, who feared a whitewash from the monitoring team, have been angered by the general's comments, which they say "didn't really acknowledge" the harsh reality facing anti-government protesters in Syria.

"We placed our hopes in the entire Arab League," said Homs resident Omar, who is an activist. "But these monitors don't seem to understand how the regime works. They don't seem interested in the suffering and death people have faced.

"We felt like we were shouting into a void."

Human rights groups estimate that at least 5,000 people have been killed over the past nine months since Syrian President Bashar al-Assad began a brutal crackdown on protesters.

A third of the fatalities were reportedly in Homs.

The US State Department condemned what spokesman Mark Toner called an escalation of violence in Homs before the monitors' arrival.

"We have seen horrific pictures of indiscriminate fire, including by heavy tank guns, and heard reports of dozens of deaths, thousands of arrests, as well as beatings of peaceful protesters," Toner said.

"The monitors should have unfettered access to protesters and to areas most severely affected by the regime's crackdown. They bear a heavy responsibility in trying to protect Syrian civilians from the depredations of a murderous regime.

"If the Syrian regime continues to resist and disregard Arab League efforts, the international community will consider other means to protect Syrian civilians."

Foreign media's lack of access to the country has made it difficult to verify varying accounts about the severity of the situation.

Although the protests have been intense in Homs and several other cities, it is unclear how widespread anti-government sentiment is throughout the country.