At least 12 people were killed and 20 injured when a powerful explosion rocked a commercial hub in Bangkok on Monday, media reported.The blast took place close to Erawan Shrine in the Thai capital, local TV reported while quoting police as saying it was caused by a bomb.The attack took place in the capital's central Chidlom district.Local TV showed burnt motorbikes on the main road, with paramedics and police trying to take the injured away.The explosion was on the Rajprasong intersection, which has been the centre of political demonstrations in recent years.