ALEPPO – A Syrian army helicopter fired machinegun rounds and troops shelled rebel positions in Aleppo Saturday. Earlier in the day, Syrian forces clashed with rebels around Aleppo's television and radio station, activists said, and a local rebel commander said his fighters were preparing for a “strong offensive” by government forces on the city. Heavy explosions shook Damascus Saturday and helicopters circled overhead as fighters appeared to be renewing their offensive in the city. The fresh battles show that President Bashar Assad's victories could be fleeting as armed opposition groups regroup and resurge, possibly forcing the regime to shuffle military units to react to attacks across the country. The country's civil war has intensified in recent weeks as fighters focused on the country's two biggest cities, Damascus and Aleppo. The two cities are crucial prizes for both sides in an increasingly brutal struggle that has eluded all attempts at a diplomatic solution and risks igniting a wider conflagration. The fighting in Damascus appeared likely to drain the army's resources as fighting stretches into its second week in Aleppo, 350 km to the north. As the fighting grinds on, Syria reached out to its powerful ally Russia Friday. Senior Syrian officials pleaded with Moscow for financial loans and supplies of oil products — an indication that international sanctions are squeezing Assad's regime. Syria is thought to be burning quickly through the $17 billion in foreign reserves that the government was believed to have at the start of Assad's crackdown. Deputy Prime Minister Qadri Jamil, who has led a delegation of several Cabinet ministers to Moscow over the past few days, told reporters Friday that they requested a Russian loan to replenish Syria's hard currency reserves, which have been depleted by a US and European Union embargo on Syrian exports. In Aleppo's battleground Salaheddine district, rebels from the Free Syrian Army hid in alleyways, dodging the Syrian army's bullets and tank rounds that struck a building in the district Saturday. “There is one helicopter and we're hearing two explosions every minute,” a Reuters reporter said. A Syrian activist told Reuters the fighters had earlier sought to extend their area of control from the Salaheddine district, where the most intense fighting has been focused, northwards to the area around the television and radio station. As fighting raged on, about 650 Syrians, including a defecting brigadier general, fled to Turkey in the past 24 hours, a Turkish official said Saturday. The latest group brought the number of Syrian refugees in Turkey to 46,000, said the official, who requested anonymity. The official declined to give the exact number of defected generals currently in Turkey, saying that some had been going back across the border to join in the fight against Assad's regime. They are estimated to be more than 20. Senior Syrian officers have been crossing into Turkey to link up with the rebel Free Syrian Army on a near daily basis in recent months, often accompanied by rank-and-file troops. In addition to taking in refugees, Turkey is also sheltering Syrian military defectors in a separate camp near the border where security is tighter. – Agencies