BANGKOK - Thailand has put over 460 locations across Bangkok on high alert on Friday in response to a series of grenade attacks that have rattled nerves in a city still under emergency rule after deadly protests.

Royal palaces, key government buildings, power plants and public transport will receive special protection from the Centre for Resolution of Emergency Situation (CRES), the body set up to monitor security since unrest in April.

Thousands of police, soldiers and city officials will swell Bangkok's security presence so that streets can be patrolled around the clock, starting late Friday.

"Government will mobilise thousands of personnel from the armed forces and police, both in uniform and plain clothes," CRES spokesman Major General Piya Uthayo said.

He said 130 locations, including those already targeted, were considered extremely high risk and continual patrols would operate within a 400 metre (1,320 feet) radius.

A further 198 places, such as the homes of key public figures, have been placed on a second level of high alert and will have checkpoints guarding access.

A third level of alert will be enforced at 136 locations such as banks and department stores, which will receive additional training for their private security staff.

Bangkok authorities now plan to upgrade thousands of security cameras across the city, boosting storage capacity so that images can be saved for one month.

Five bombings in little over a month, leaving one dead and thirteen injured, have unnerved Bangkok residents still recovering after April and May's "Red Shirt" protests.

The blasts - at targets including Thailand's national TV centre and an apparent repeat attack at the King Power duty-free shopping outlet - have also raised doubts over the speed at which emergency laws can be lifted in Bangkok.

The capital is one of seven areas still under the special rules introduced on April 7 as a response to the Red rallies that later left 91 people dead and about 1,900 injured in clashes between protesters and the army.