BEIJING — A suicidal man started a fire on a bus in China that killed 47 people, state media said on Saturday, a disaster that came just days after 120 people died in a fire at a poultry plant.

The bus caught fire during the rush hour on Friday as it was on elevated tracks in the coastal city of Xiamen, the Ministry of Public Security said, labeling it a "serious criminal case."

State television said Xiamen resident Chen Shuizong started the fire. A suicide note was found at his home and he was among those killed, it said.

"Chen Shuizong felt his life was not as he wished it and he was profoundly pessimistic, so he gave vent to his anger by setting the fire," the television added in a brief report.

On Monday, a fire at a poultry slaughterhouse in northeastern China killed 120 people. Authorities said safety management at the plant was a "total mess" and have detained two executives.

President Xi Jinping, visiting California for a summit with U.S. President Barack Obama, demanded his government pay closer attention to preventing fires, the Xinhua news agency said.

"Life is precious, and lives cannot be sacrificed in the pursuit of development," it cited him as saying. "Lessons must be learned from this spilling of blood and bitter experience."

Buses have been targeted before in China.

In 2009 a passenger lit petrol on a bus in Chengdu, killing 27 people and injuring dozens. Also that year, 24 people died in a shuttle bus fire in Wuxi, near Shanghai, started by a disgruntled steel worker.

In 2005 a 42-year-old farmer with terminal lung cancer set off a crude bomb on a bus in a suicide attack that wounded 31.