A strong explosion rocked the Syrian capital Thursday near a busy market and the country's highest court, wounding at least three people and sending clouds of black smoke into the sky. The blast came as tensions threatened to spread across the region. Neighboring Turkey deployed anti-aircraft guns and other weapons alongside its border with Syria, nearly a week after Syrian forces shot a Turkish military plane out of the sky, Turkish state TV said Thursday. Major world powers will meet Saturday in Geneva for talks on Syria, but few observers expect a major breakthrough. Syria has the protection or Russia, a veto-wielding member of the U.N. Security Council, and has so far been impervious to international pressure. Russian Foreign Minister Sergey Lavrov said Thursday that Moscow will not endorse a call for Assad to give up power. It was not clear who was behind Thursday's blast in Damascus. An Associated Press reporter at the scene of the blast said some cars were charred and many had their windshields blown out. Elsewhere in Syria, activists reported clashes between troops and rebels and said more than a dozen people were killed nationwide. Some of the heaviest battles were in the eastern city of Deir el-Zour, activists said. Activists say more than 14,000 people have been killed since the Syrian uprising began in March 2011. Turkey, a former ally, has become one of the strongest critics of the Assad regime. Tensions between the two countries spiked following the downing of the Turkish plane last week. Syria insists the Turkish military plane violated its air space on Friday. Turkey says the jet had unintentionally strayed into Syria's air space and was inside international airspace when it was brought down over the Mediterranean by Syria.