A Chinese court sentenced a woman to death and jailed her husband for life for lacing milk with nitrite that killed three children and made 36 sick, state media reported on Friday.

Ma Xiuling and Wu Guangquan, two dairy farmers from Pingliang in northwestern Gansu province, were found to have deliberately added nitrite, an industrial salt, to fresh milk produced by their business rivals in early April, Xinhua said, citing a spokesman with the Pingliang Municipal Intermediate People's Court.

Ma and Wu committed the act as a form of revenge against their rivals, another couple, in the wake of several business disputes, the spokesman added.

The three children who died after consuming the tainted milk were under two years old.

The Xinhua report said the couple was appealing against the verdict.

That ruling came just days after Chinese police in northeastern Jilin province said they believed a child who died after drinking a yogurt drink was probably the victim of deliberate poisoning.

Food scandals are common in China, where crackdowns have failed to stamp out poisonings and toxin outbreaks that have shaken consumer confidence. The fast-growing but fragmented dairy sector has been at the heart of those worries.

In 2008, at least six children died and nearly 300,000 became ill from powdered milk laced with melamine, an industrial chemical added to low quality or diluted milk to fool inspectors by giving misleadingly high readings for protein levels.

(Reporting by Sui-Lee Wee; Editing by Ken Wills)