Authorities said one man was slightly injured after a pair of improvised bombs went off near a luxury shopping mall in central Bangkok on Sunday. The improvised explosive devices (IEDs) were set for one of the busiest times at Siam Paragon mall, which is frequented by tourists and locals. Police spokesman Lt. Gen. Prawut Thawornsiri said authorities believe the explosions were not intended to kill anyone but only cause disruption at an elevated train station outside the mall, where the bombs had been placed. "The explosions were caused by two pipe bombs, but the flash powder that was used had low pressure," he said. "It showed the perpetrators intended only to cause panic, threaten or stir up chaos." Investigators did not identify any suspects and did not rule out political motivations, but the bombs are the first sign of violence the country has seen since a military coup seized power and implemented martial law last May. The explosions come a week after the retroactive impeachment of former Prime Minister Yingluck Shinawatra for her mishandling of a rice subsidy program. Junta-leader-cum-Prime Minister Prayuth Chanocha said on Monday authorities are tightening security in public places following the bombing.