Two unknown perpetrators vandalized a pair of outdoor statues at the newly-opened outpost of Taiwan’s National Palace Museum in the southern city of Chiayi on Wednesday night.

The artworks—which had been donated by the actor Jackie Chan, born in Hong Kong and known for his pro-China stance—were covered with red paint and the anti-China slogan “cultural united front” had been written on their bases.

The slogan is used in Taiwan to criticize China’s attempts to exercise more political influence over the island of Taiwan, which has been independent since the end of the 1949 Chinese civil war.

Depicting a dragon and a horse head, the bronze statues are replicas of famous Qing Dynasty artworks and are symbolic of China’s suffering under foreign oppression. The original 12 zodiac head statues were looted by Anglo-French troops in the 1860.

The museum, famous for its extensive collection of historic Chinese art and artifacts, condemned the attack.

“A large part of the National Palace Museum’s collection originates from the Qing imperial collection, that is Chinese cultural pieces,” a statement issued by the museum said. “If exhibiting relics related to Chinese culture is considered ‘united front,’ how can the [museum] continue to operate?”

According to AFP, preliminary investigations by local police have found that the vandalism was carried out by a man and a woman.

Political tensions between Taiwan and mainland China have been on the rise, and statues symbolic of Chinese rule have frequently been targeted by nationalist Taiwanese activists, who remain deeply suspicious of Chinese attempts to regain control of the region.

The museum said the statues had already been cleaned, and that added security had been implemented to protect them.