Security guards stand in line while pupils play beside a primary school in Nanjing, Jiangsu province, on Friday. (Sean Yong/Reuters)

A spate of recent killings at primary schools in China can be blamed on deep-seated social tensions, Chinese Premier Wen Jiabao says.

The premier's comments, made Friday during an interview with Hong Kong's Phoenix Television, are the first official suggestion that the killings aren't simply the acts of deranged men.

Fifteen children have been killed and 80 others injured by men armed with cleavers, hammers or knives on five occasions since March.

Chinese Premier Wen Jiabao, seen here on March 22, 2010, has said the social tensions behind a spate of recent school killings should be addressed. (Feng Li/Reuters)

Most recently, a 48-year-old disgruntled landlord killed seven children and wounded 11 others with a meat cleaver Wednesday at a kindergarten in Hanzhong, in northwestern China. He then went home and committed suicide, the local government reported.

Chinese media have portrayed the incidents as random killings committed by insane men.

But China also needs to take a good look at addressing the deep-seated causes behind the killings, including dealing with social conflicts and resolving disputes, Wen said.

Though the Communist Party has liked to say it's building a harmonious society, the country's rapid economic transformation has brought with it an enormous gulf between rich and poor. Corruption is also rampant, and people who seek justice through legal channels often don't find it.

Schools nationwide have increased security since the killings began, installing gates and security cameras. Some schools have also posted additional police and guards at entrances.

"Innovation in the management of society is not only essential but urgent," said Wu Heping, China's minister in charge of public security, the BBC reported.

"I have noticed the central government's demand for the public security bureaus, under the leadership of all levels of local government, to properly handle the various conflicts in society," Wu reportedly said.

Security measures aren't enough, Wen said, adding the government needs to "handle social problems, resolve disputes and strengthen mediation at the grassroots level."

Other killings

It was not clear if security had been beefed up at the school attacked Wednesday.

The assaults began with an attack on a primary school in March in the city of Nanping in Fujian province, where eight children were killed by a former medical worker with a history of mental health problems.

The man convicted for that crime was executed on April 28, the same day a 33-year-old former teacher broke into a primary school in the southern city of Leizhou in Guangdong province and wounded 15 students and a teacher with a knife.

The next day, a 47-year-old unemployed man armed with a knife wounded 29 kindergarten students — five seriously — plus two teachers and a security guard at a school in Jiangsu province.

Just hours later, a farmer hit five elementary students with a hammer in the eastern city of Weifang before setting himself on fire.

With files from The Associated Press