Bangkok, Thailand: Thai Prime Minister Prayuth Chan-ocha ordered security to be tightened in Bangkok on Monday after two small bombs rattled a luxury shopping mall and stoked tension in a city under martial law since a coup in May.

Two people were slightly hurt but the blasts caused little damage on Sunday evening. They were the first to shake the capital since the military seized power to end months of sometimes deadly street protests.

“I have ordered security to be tightened because this case involves the well-being of the people," Prayuth told reporters.

“This case shows that we still need martial law ... there are still bad people disrupting the peace. We must find ways to severely punish them”.

There was no claim of responsibility.

CCTV footage showed two possible suspects near where the pipe bombs exploded in the heart of one of Bangkok's busiest shopping districts but the images were unclear and they had not been identified, police said.

Political tension has been high since last month when a national assembly hand-picked by the junta banned former Prime Minister Yingluck Shinawatra from politics for five years.

The decision angered supporters of Yingluck and her self-exiled brother, Thaksin Shinawatra, although there has been little sign of a return to the protests that have dogged Thailand for years. The military has been tough on dissent since the coup.

The bombs were just a few hundred meters away from the site of a military crackdown on ‘red shirt’ supporters of the Shinawatras in 2010.

The motive for the Sunday blasts appeared to be to create panic, said junta spokesman Winthai Suvaree. The bombs were behind power transformers on a walkway linking an overhead rail line to the Siam Paragon mall, police said.