Syrian protesters pour into city

Tens of thousands of Syrians carrying olive branches and calling for the downfall of President Bashar Assad's regime have poured into the flashpoint city of Hama, where the US and French ambassadors travelled in a strong show of support for the protest movement.

Mass demonstrations also erupted in cities and towns nationwide, triggering a crackdown that killed at least five people, activists said.

Two witnesses in Hama said crowds were swelling in the central city, which has become a focal point of the uprising and has drawn the largest crowds since the revolt began nearly four months ago.

"People are chanting: 'We only kneel to God,' one of the witnesses told the AP by telephone.

Hama poses a potential dilemma for the Syrian regime because of its place as a symbol of opposition to the rule of the Assad family.

In 1982, the late Hafez Assad ordered troops to crush a rebellion by Islamist forces, killing between 10,000 and 25,000 people, rights activists say.

A major offensive could make the city a fresh rallying cry for the opposition, but Assad's regime also does not want a repeat of last Friday's stunning rally, when an estimated 300,000 people protested.

The US and French ambassadors travelled to Hama on Thursday and left today before the protests began.

US Ambassador Robert Ford's trip drew strong condemnation from the Syrian government, which said the visit was unauthorised and a clear sign that Washington was inciting unrest.

Relations between the US and Syria are chronically strained over Assad's close ties with Iran.

"The presence of the US ambassador in Hama without obtaining prior permission from the Foreign Ministry as stipulated by instructions distributed repeatedly to all the embassies is clear evidence of the US involvement in the ongoing events in Syria," the state-run news agency reported.

The US is trying to "aggravate the situations which destabilise Syria", the statement said.

In Washington, State Department spokeswoman Victoria Nuland said Ford "spent the day expressing our deep support for the right of the Syrian people to assemble peacefully and to express themselves".

Ford reached the city after passing checkpoints run by the military and Hama residents. Nuland said he met nervous residents and saw many shops closed because of a protest-linked strike. He also visited a hospital treating the wounded.

The Syrian government did not comment on French Ambassador Eric Chevallier's trip to Hama.

France's Foreign Ministry said in a statement that Chevallier's visit shows "France's concern for the Syrian population ... (France) denounces the pursuit of violence and arbitrary arrests and the absence of a credible commitment from the Syrian authorities to a political reform process."

Hama residents have shut down the city in recent days, going on strike and trying to prevent security forces from entering by setting up checkpoints of tires and concrete blocks.

Still, the London-based Syrian Observatory for Human Rights said 21 people have been killed there since Tuesday.