At least 28 people have been injured in two explosions in Bangkok in the latest attack on protesters demanding the resignation of Prime Minister Yingluck Shinatwtra.

The attack took place on Sunday, hours after an anti-government activist was wounded when a gunman opened fire at protesters shortly before midnight on Saturday.

The Erawan Medical Center said the injured were taken to four different Bangkok hospitals.

It was not immediately clear what caused the explosions.

The protesters, who control several small patches of the city, are vying to overthrow Yingluck's government.

While the day-time protests have been largely calm in Bangkok, assaults have been reported nightly, including shooting attacks at protest venues and small explosives hurled at the homes of high-profile protest supporters.

Protesters also want to derail February 2 elections, called by Yingluck in a bid to quell the crisis.

On Friday, an explosive device hurled at a crowd of marching demonstrators in another part of Bangkok killed one man and wounded dozens of people.

Police said the blast was caused by a fragmentation grenade.

Divided society

The Southeast Asian nation has been wracked by repeated bouts of unrest since the military deposed Yingluck's brother, former Prime Minister Thaksin Shinawatra, in 2006 amid charges of corruption and alleged disrespect for the monarchy, which he denies.

The coup touched off a societal schism that in broad terms pits the majority rural poor who back the Shinawatras against an urban-based elite establishment supported by the army and staunch royalists who see Yingluck's family as a corrupt threat to the traditional structures of power.

Yingluck's opponents, a minority that can no longer win at the polls, argue the Shinawatras are using their electoral majority to impose their will and subvert democracy.

The crisis boiled over again late last year after the ruling party attempted to push through an amnesty bill that would have allowed Thaksin to return from self-imposed exile. Thaksin has lived abroad since 2008 to avoid a prison sentence for a corruption conviction.

Yingluck has ordered police to go out of their way to avoid confrontations with protesters.

The strategy is aimed at averting violence, but it also has undermined rule of law and the government's authority, with police staying away from the scattered pockets of Bangkok controlled by demonstrators.

Source: Agencies