For Turkish firms exporting marble and other stone to an increasingly lucrative Chinese market, the Xiamen International Stone Fair should have been the business highlight of the year. Instead, the arrest and detention of four Turkish executives for tax evasion sent scores of others fleeing, grabbing any flight they could from mainland China for fear they might be next.

Turkey's Hurriyet Daily News reported widespread panic among attendees. One vowed never to return to China, saying he was lucky to find a place on the first plane out.

It appeared to be a deliberate and brutal reminder by Beijing of the economic costs of Turkey's February criticism of China for the treatment of its Muslim Uighur minority. With a U.N. panel last year accusing Beijing of interning up to a million Uighurs in so-called re-education camps, it's a topic many in the rest of the world feel they can no longer quietly ignore.