BEIRUT – Turkey deployed anti-aircraft guns, rocket launchers and other weapons along its border with Syria on Thursday, a military buildup that came as world powers showed new urgency to resolve the crisis before it ignites the region.

A bomb exploded in central Damascus near a busy market and the country’s main justice complex, wounding at least three people, damaging cars in a parking lot and sending a black cloud rising above the Syrian capital. It was not clear who was behind the bombing.

Much of the violence that has gripped Syria since the uprising began in March 2011 has been sanctioned by the government of President Bashar Assad to crush dissent. Activists say more than 14,000 people have been killed.