Seoul (CNN) -- A pastor and his wife are in custody accused of killing three of their children by starving them to ward off evil spirits, police in South Korea said Wednesday.

The couple told police the children -- aged nine, seven and three -- had been ill, which they believed was a sign they were invaded by evil spirits after eating too much on Lunar New Year.

They then cut the children's hair to chase the spirits out and starved them from January 24 until February 2, only allowing them to drink water. Local media reports said the parents had beaten the children with a belt and a fly swatter numerous times.

The pastor, named only by his surname Park, and his wife, Cho, told police they tied the children's arms and legs with stockings. All three died on February 2, the first around 2am, the second at 5am and the third at 7am, according to police in the town of Boseong, more than 186 miles (300 kilometers) south of Seoul.

The bodies were found nine days later by Park's brother-in-law. Police said the couple was praying in the hope of resurrecting the children. Their eight-month-old daughter who survived has been taken into care, police said.

Park, 43, and Cho, 34, told police they opened a church in Boseong in March 2009 with a congregation of 10, but were accused of being a cult.

The police plan to forward the case to the prosecutor's office on February 17.

Journalist Yoonjung Seo contributed to this report.