Catherine Turner reports on Syrian protests continuing despite the military's deadly crackdown.
The International Committee of the Red Cross has urged Syria to lift restrictions on access to casualties in the besieged city of Deraa, amid mounting international pressure on the Syrian regime to end its violent crackdown on protests.
Deraa has been the epicentre of anti-government unrest with protesters demanding an end to Assad's presidency and the Baath Party's near-50-year rule.
Soldiers and tanks have been deployed there and in other cities in a security crackdown which activists say has claimed hundreds of lives.
"The violence has resulted in a large number of casualties and we fear that if the situation worsens, more lives will be lost," Marianne Gasser, head of the International Committee of the Red Cross (ICRC) delegation in Damascus, said on Tuesday.
"It is urgent that emergency medical services, first aid workers and others performing life saving tasks swiftly reach those in need," she added in a statement.
ICRC spokesman Hisham Hassan said the doctors and staff from the agency Syrian Red Crescent and other medical workers needed "immediate access to the injured".
"So far we have had restricted access to certain areas, however today we need to have more larger access especially in the south, and here I talk about Deraa," he told journalists.
"We are in touch with Syrian authorities on a daily basis but so far what we have been able to get is access probably tomorrow or the day after to certain hospitals in rural Damascus, but so far no news about Deraa in the south."
In a statement released on Tuesday, Amnesty International said it had received "first-hand reports of torture" from those caught up in the crackdown.
"Detainees who were recently released told the organization of beatings and harsh conditions in detention, raising fears for the safety of hundreds of others being held, including at least 499 people who were arrested on Sunday in house-to-house raids in the southern town of Deraa," the organisation said.
"These disturbing new accounts of detainees being tortured further underscore the need for President Bashar al-Assad to put an end to his security forces’ violent onslaught against his own people," said Philip Luther, Amnesty International’s Deputy Director for the Middle East and North Africa.
Syria's government accuses "armed groups and terrorists" of attempting to stir unrest in the country.
Syrian security forces swept into the coastal city of Baniyas on Tuesday, a protest leader told the Reuters news agency.
"They moved into the main market area. The army has sealed the northern entrance and security forces [sealed] the south," said Anas al-Shughri. "They armed Alawite villages in the hills overlooking Baniyas and we are now facing militias from the east."
International condemnation of the crackdown has intensified since the Deraa assault, which revived memories of the 1982 repression of an armed Islamist uprising in the city of Hama by Assad's father, president Hafez al-Assad.
In-depth coverage of escalating violence across Syria
"Syria should not go through another massacre like Hama. We have reminded them of this," Recep Tayyip Erdogan, the Turkish prime minister, who has sent envoys to Damascus and spoken to Assad several times during the unrest, told Turkey's A-TV channel.
A US State Department spokesman, Mark Toner, on Tuesday described the crackdown in Deraa as "barbaric" and expressed concern about the humanitarian situation in the city.
"These are, quite frankly, barbaric measures and they amount to the collective punishment of innocent civilians," Toner said.
France, Germany and the UK said they were seeking the imposition of European Union sanctions on Syrian leaders including Assad.
"We are trying to act with our European partners," Alain Juppe, France's foreign minister, told reporters. Asked if Assad should be included among targets of sanctions, he said: "That's what France wants."
Werner Hoyer, Germany's deputy foreign minister, also said it was time for action.
"The Syrian government's continuing brutal actions leave the European Union no choice but to press firmly ahead with targeted sanctions against the regime," he said.
Addressing parliament on Tuesday, William Hague, Britain's foreign minister, said: "We are now working with our European partners on targeted sanctions, on asset freezes and travel bans. I will be discussing those further with the French foreign minister this evening."
Ehud Barak, Israel's defence minister, said that the "brutality" of al-Assad's response to the protests would lead to the downfall of his regime.
"I think that Assad is approaching the point where he will lose his internal legitimacy," Barack told Israel's Channel 10 television on Monday night.
"Even if he stops the bloodshed, I don't think he can restore his legitimacy. He may recover, but in my opinion it won't be the same and he is destined to meet the same fact as the leaders of other Arab countries shaken by uprisings."
More than 1,000 people have been arrested in their latest security sweep, according to a prominent human rights activist.
Ammar Qurabi, the head of the National Organisation for Human Rights in Syria, said on Tuesday that his group had documented about 1,000 names of people who had been detained across the country's provinces in door-to-door raids since Saturday.
He said many other people had been reported missing.
Pro-democracy protesters have called for permanent sit-ins across Syria from Tuesday.
"We call on Syrians in all regions to gather from Tuesday evening in all public places to organise sit-ins which will continue day and night," said a Facebook post by the opposition Syrian Revolution 2011 website.
Al Jazeera is demanding information about one of its journalists who has been missing in Syria since Friday.
Dorothy Parvaz left Doha, the Qatari capital, for Syria to cover events in the country. However, there has been no contact with the reporter since she disembarked from a Qatar Airways flight in Damascus.