A man reportedly admitted sending bombs to three doctors who failed to cure him and his three sons of a sexually transmitted disease.
Sichuan native Li Shikang and his brother-in-law, Chen Deshun - both arrested this month - told police they concealed the bombs as gifts, the Beijing Morning Post reported. The devices killed six people and injured 17.
Li caught the disease from prostitutes. The paper did not identify his illness.
He sought medical help for the boys in 1997 but when they got worse, Li blamed the doctors for not fulfilling their duties and decided to seek revenge.
A doctor and two others died when a 'gift' exploded at the Guangzhou Nanfang Medical Centre in Guangdong on October 6. There was another explosion when a bottle of liquor given to a doctor was opened in a Zhuhai restaurant on October 24, killing the waitress who opened it and a bystander. Another medic died when a bomb was sent to his home.