Officials in Beijing say 16 Chinese fishermen who were seized for ransom in North Korea have been released.
China's Foreign Ministry said the men and their fishing boat were returned safely on Tuesday. It added that no ransom was paid.
The owner of the boat says the North Koreans were demanding nearly $100,000 for the return of the boat and crew, which were taken May 6 in the waters between China and the Korean peninsula.
It remains unclear who in North Korea was responsible for the kidnapping. Chinese Foreign Ministry spokesperson Hong Lei said Beijing wants an explanation.
"We hope that the North Korean side can launch a full investigation into this related incident, give an explanation to the Chinese side, and also take effective measures to prevent a recurrence of such events," said Hong.
The incident has prompted an angry reaction on China's microblogs, and threatens to upset already tense diplomatic relations between the two allies.
Relationship getting sour
Before the release, the Global Times, the mouthpiece of China's Communist Party, said in a Tuesday editorial that Beijing should "let the North Korean side know we are angry."
If North Korea continues to "go rogue," the editorial said, China should "take actions to push it toward a more measured response." Pyongyang is heavily reliant on Beijing for economic aid and diplomatic support.
There are other signs the relationship is beginning to sour. Earlier this month, the state-run bank of China halted business with North Korea's main foreign exchange bank, in a move seen as a toughening of Beijing's stance against Pyongyang's nuclear weapons program.
It is not the first time Chinese sailors have been held in Pyongyang. A year ago, unidentified North Koreans detained 29 fishermen and a number of vessels for weeks and unsuccessfully demanded a ransom before releasing them.