Series of explosions kill four and wound at least 20 others

Devices hidden in potted plants and went off within 30 minutes of each other in the bar district of the city

Tourist areas including the resort town of Hua Hin targeted

A wave of coordinated explosions rattled multiple cities across southern Thailand, killing at least four people and wounding dozens more. Among the injured were 11 foreigners in the seaside resort town of Hua Hin.

It was not clear who was behind the attacks, but police said the violence was not linked to Islamic terrorism.

The timing and scope suggested the bombs were set off by opponents of the Southeast Asian nation's ruling junta, which last weekend organized a successful referendum on a constitution that critics say will bolster the military's power for years to come.

Friday is also a public holiday in Thailand to mark Queen Sirikit's birthday.

Police said four of the injured tourists were from Germany, two from Italy and one from Austria. The Netherlands said four of its citizens were also wounded.

Britain and Australia reacted to the news by advising their nationals to avoid public places.