BEIJING - Four people were killed and 19 injured Friday in a blast at a tax office in central China that police said appeared to be a deliberate attack, state media reported.

The explosion went off at about 4.15 pm on the third floor of a district tax office in Changsha, capital of Hunan province, Xinhua news agency said, quoting a police statement.

According to police, initial investigations indicated it was a planned attack, Xinhua said. The report gave no details of possible suspects or the motive for the attack.

Police sealed off the building in central Changsha and blocked nearby roads for investigation after workers were evacuated, Xinhua said.

All the windows on the third floor were shattered and large blood stains could be seen on the stairs, the news agency said.

China sees thousands of cases of violent social unrest each year, typically as marginalised segments of society lash out over illegal seizures of their land, environmental degradation, government corruption or other grievances.

Separately, in the northeastern province of Jilin, one person was killed and 20 injured in a series of blasts at a barber's shop, Xinhua said.

Four firefighters were among those injured in the explosions which occurred around 4.45 pm Friday in the provincial capital Changchun.

Firefighters and workers from a gas supply company were at the site, it said.

Police were investigating the cause of the explosions.