Syrian tanks and armored vehicles swept into the coastal city of Latakia on Saturday and gunfire was heard in a district where thousands had protested against President Bashar Assad, an activist group said.The deployment took place a day after security forces shot dead 20 people during nationwide marches in which demonstrators called for Assad’s overthrow and vowed to “kneel only to God.”Syria would be better off without Assad, US Secretary of State Hillary Clinton said on Friday. She 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.Around 20 military vehicles deployed on Saturday near the Ramle district in Latakia, where 10,000 people had demonstrated on Friday, the British-based Syrian Observatory for Human Rights 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 tons 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. More than 150,000 Avaaz members had signed a petition to that effect, it said.Meanwhile, Turkish President Abdullah Gul warned Assad not to leave reforms until it is too late, in a letter delivered to the Syrian president last week, Turkey’s state-run Anatolian news agency reported on Friday.Part of a campaign of Turkish pressure on Syria, for whom Turkey has been an important ally, the letter was delivered by Foreign Minister Ahmet Davutoglu when he visited Damascus and held talks with Assad on Tuesday.“I don’t want to see you looking back one day and regretting that what you have done was too little and too late,” Anatolian quoted Gul as writing in the letter, saying Turkish people were saddened by the bloodshed in Syria.“Leading the change instead of being carried away by the winds of change will place [you] in a historical position,” Gul wrote.Davutoglu demanded last week that Syria’s leaders stop the killing of civilians involved in unrest against Assad’s autocratic rule, saying events in the coming days would be critical.Activists say more than 1,700 civilians have been killed in the counterinsurgency so far.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, US Ambassador to Damascus Robert Ford said more sanctions would follow if the Syrian authorities did not halt the violence.