DAMASCUS - Syrian troops Monday reclaimed most of Damascus after a week of heavy clashes.Fighting was still raging in Syria’s second-biggest city of Aleppo, however, as rights activists reported that violence across the country killed at least 52 people, including 24 civilians.And President Vladimir Putin of Russia, the Syrian regime’s main international ally, warned of a protracted civil war should rebels be allowed to remove President Bashar al-Assad from power.Kassem Saadeddine, spokesman for the joint command of the rebel Free Syrian Army (FSA), said Makdissi’s remarks gave cause for concern. “The regime admits having chemical weapons, and as it has not signed any treaties, that proves that it will not hesitate to use them,” Saadeddine told AFP.On Monday, the United States warned Syria. “They should not think one iota about using chemical weapons,” Pentagon press secretary George Little told reporters.The White House has said Washington would “hold accountable” any Syrian official involved in the release or use of the country’s chemical weapons.UN chief Ban Ki-Moon said that the use of chemical weapons in Syria would be “reprehensible” after Damascus raised the possibility of using such arms if there was an attack from outside. “It would be reprehensible if anybody in Syria is contemplating (the) use of such weapons of mass destruction like chemical weapons,” Ban told reporters in Belgrade on the fourth leg of his Balkans tour.Putin warned of a protracted civil war in Syria should rebels be allowed to remove Assad from power. “We are afraid that if the country’s current leadership is removed from power unconstitutionally, then the opposition and today’s leadership may simply change places,” Interfax news agency quoted Putin as saying.Iraq also rejected the Arab League call for Assad to step aside, describing it as interference. Prime Minister Nuri al-Maliki, meanwhile, instructed Iraqi forces and the Red Crescent to allow in Syrian refugees and provide them with support, reversing an earlier decision.Makdissi also vowed Syrian forces would soon regain control of several border posts that rebel forces seized along the frontier with Iraq and Turkey. The rebels “will not hold onto them and they will be gone in a few days,” he said.On the ground, government forces reclaimed most of Damascus, after a week of heavy fighting with rebels, who remain in the city but are planning a guerrilla strategy, activists and regime sources said.An activist who identified himself as Ahmed told AFP via Skype that “the battle to liberate Damascus continues, and there is still fighting in several areas of the city.” A security source in Damascus confirmed the city had been reclaimed by government forces. Elsewhere, rebels and troops clashes violently in Syria’s commercial hub Aleppo, where the rebel FSA says a war of “liberation” is also underway.Clashes engulfed the eastern Sakhur and Hanano City districts, leading residents to flee the areas, said the Syrian Observatory for Human Rights.Regime troops also used helicopters to pound the central city of Homs - symbol of the uprising - and nearby rebel-held Rastan, activists said. The Britain-based Observatory says more than 19,000 people have been killed since the uprising began in March 2011.As tens of thousands of Syrians flee escalating war and chaos, the EU looked at ways of boosting humanitarian relief and beefed up sanctions and an arms embargo against the regime Monday.Joining talks with their European Union counterparts, the foreign ministers of Britain, France and Sweden called for a hike in aid to Syrians who have fled to safety in neighbouring Jordan, Lebanon and Turkey.“We have to step up humanitarian assistance for the people fleeing,” said British Foreign Secretary William Hague, as France’s Laurent Fabius and Sweden’s Carl Bildt demanded the EU “do more” to help Syria’s neighbours cope with the influx.Brussels meanwhile announced it was increasing by 20 million euros its emergency aid to Syrian refugees to total 63 million euros. Meanwhile, President Michel Sleiman on Monday accused Syria of violating Lebanese territory after a house in the east of the country was hit by a blast and shells fell on the northern border. In a rare protest against Syria, the Lebanese president “has asked Foreign Minister Adnan Mansour to send a letter to Syria’s ambassador to Lebanon, addressing the Syrian authorities, to protest this issue,” a statement said.Sleiman “expressed his displeasure” after a house in the eastern Qaa region was hit by a blast and shells fired from Syria slammed into several villages along the northern border.A security official told AFP that “unknown people from the Syrian side infiltrated into Lebanon on Sunday in the region (of Qaa) and blew up the house of Jamal Ghadada, on the Syrian-Lebanese border, after mining it.”Sleiman “also asked the army command and the relevant authorities to coordinate... in order to avoid a repetition of these violations once and for all,” according to the statement.The protest was the first of its kind by a Lebanese president since Syrian troops withdrew from Lebanon in 2005 after nearly three decades of political and military hegemony over its smaller neighbour.There has been an increase of cross-border clashes, some of them deadly, and shelling from Syria into Lebanon in recent weeks, particulary in the north and the east border areas.