Papua New Guinea has been accused of bowing to pressure from mainland China by downgrading relations with Taiwan.
Taiwan's government says China forced PNG to change the name of Taipei's representative office in the country and remove diplomatic licence plates from its representatives' cars.
Taiwan and PNG don't have formal diplomatic relations, but Taiwan opened a trade office there in 1990.
In a statement on Sunday, China's Foreign Ministry noted the name of Taiwan's PNG office had been changed to the Taipei Economic and Cultural Office in PNG.
China, which is an increasingly influential partner of PNG's government, said it appreciated the move.
The Reuters news agency reported Taiwan's government called the move "insensitive" and "deeply regrettable", considering Taiwan is still dealing with the aftermath of a deadly earthquake.
Taiwan's Foreign Ministry said the move had hurt the feelings of Taiwanese people, and even caused a backlash.