Among the missing items are an altar cross or crucifix, two candlesticks and three wooden sculptures from the 13th and 14th centuries.
The sculptures, which newspaper Östgöta Correspondenten described as “priceless” on its website on Monday, depict the Virgin Mary and St. Catherine.
“The large losses are the medieval sculptures,” Jan Eriksson, curator at the Östergötland county museum, told the newspaper.
The wooden church, which belongs to the Linköping diocese headquartered nearly 70 km away, dates from the 1200s and is one of Sweden’s few remaining medieval wooden churches.
The thieves were apparently knew what they were looking for and were familiar with the church, located about 10 km southwest from Kisa, a town with a population of 3,700.
The stone sacristy, or room for keeping vestments and other church furnishings, sacred vessels and parish records, dates from the late medieval period, while the church porch to the west was constructed in 1860.
The interior has fragmented paintings from the mid-14th century. The pulpit was added in 1661, while several medieval wooden sculptures are preserved.
Police are performing a forensic investigation in the church on Monday afternoon.