By Dominic Evans
BEIRUT (Reuters) - Syrian troops killed three people as tanks swept into a coastal city on Saturday, activists said, in a crackdown on protests against President Bashar al-Assad which drew criticism from an international Muslim group.
The 57-member Organization of Islamic Cooperation, adding its voice to growing Arab pressure on Assad, called for an immediate halt to the military campaign against protesters which activists say has killed 1,700 civilians in five months.
U.S. President Barack Obama and Saudi Arabia's King Abdullah repeated their calls for the crackdown to stop.
Obama also spoke to British Prime Minister David Cameron and the leaders called for an immediate end to attacks by Syrian government forces against protesters, the White House said. It said Obama and Cameron would "consult on further steps in the days ahead." [nN1E77C03V]
Saturday's bloodshed came a day after security forces shot dead 20 people during nationwide marches in which demonstrators called for Assad's overthrow and vowed they would "kneel only to God."
The British-based Syrian Observatory for Human Rights said two people were killed and 15 wounded in heavy gunfire after around 20 military vehicles entered the Ramle district of Latakia, on the Mediterranean coast.
Soldiers backed by loyalist militia known as shabbiha were also deployed in the city's Sulaiba district, the group's head Rami Abdel Rahman said. "They are arresting dozens of people," he said, adding many people were fleeing the assault.
Troops and shabbiha killed one person in the town of Qusair, near the Lebanese border, and made arrests in nearby Jousiyah village, he said. The bodies of four people arrested during an assault last week in the Houla Plain, north of Homs city, were returned to their families, he added.
Syria has barred most independent media, making it hard to verify events on the ground in the unrest, one of a series of popular revolts against autocratic Arab leaders this year.
Authorities deny reports of deaths in detention and say 500 soldiers and police have been killed by armed groups they blame for the violence. State news agency SANA said three members of the security forces were killed in Friday's protests.
Since the start of the Muslim holy month of Ramadan in early August, Assad has stepped up the military campaign, launching army assaults on the central city of Hama and the city of Deir al-Zor in the eastern Sunni Muslim tribal heartland. Assad's family, which has ruled Syria for 41 years, is from the minority Alawite sect.
After a wave of Arab criticism of Damascus last week, the Saudi Arabia-based Organization of Islamic Cooperation (OIC) accused Syria on Saturday of using "excessive armed force" and called on Damascus to stop the bloodshed.
OIC Secretary-General Ekmeleddin Ihsanoglu urged Assad "to exercise utmost restraint through the immediate halt to the use of force to suppress popular demonstrations."
Obama and King Abdullah spoke by telephone on Saturday and "agreed that the Syrian regime's brutal campaign of violence against the Syrian people must end immediately," the White House said, adding the two leaders agreed to consult closely.
The Saudi monarch, who has had fraught relations with Assad but had worked with him to reduce tension in Lebanon last year, recalled his ambassador from Damascus on Monday.
France's Foreign Ministry advised citizens against traveling to Syria and urged any French people still in the country to leave using available commercial transport. Its website cited the "aggravation of tensions."
U.S. Secretary of State Hillary Clinton said on Friday Syria would be better off without Assad and called on nations that buy oil or sell arms to Syria to cut those ties.
"We urge those countries still buying Syrian oil or gas, those countries still sending Assad weapons, those countries whose political and economic support give him comfort in his brutality, to get on the right side of history," she said.
Syria's oil industry, with which the Assad family has close links, generates most of the state's hard currency from crude output of 380,000 barrels per day.
While Syria exports crude oil, its refinery capacity is not sufficient to meet domestic demand for fuel. Trading sources said Swiss oil traders Vitol and Trafigura agreed to supply state firm Sytrol with 60,000 tonnes of gasoline this week.
The global campaign group Avaaz urged European nations on Friday to impose immediate restrictions on purchases of Syrian oil to "dry up" funding of Assad's forces. It said more than 150,000 Avaaz members had signed a petition to that effect.
On Wednesday, Washington imposed sanctions on Syria's largest bank and its biggest mobile telephone company, controlled by Assad's cousin Rami Makhlouf. The next day, U.S. Ambassador to Damascus Robert Ford said more sanctions would follow unless the Syrian authorities halted the violence.
(Additional reporting by Alister Bull in Washington and Nick Vinocur in Paris; Editing by Janet Lawrence)