An embassy official said the Sri Lankan authorities should handle the issue in accordance with the law and release the Chinese fishermen as soon as possible, a report by China's state-run Xinhua news agency said.
Navy spokesman Cmdr. Kosala Warnakulasuriya told Xinhua that the Chinese would be handed over to police for further questioning.
The fishermen were aboard two fishing trawlers when they were spotted off the coast of Batticaloa, eastern Sri Lanka, he said.
Two Sri Lankans were arrested along with the Chinese.
A Sri Lankan police spokesman told the BBC's Sri Lankan service that the two Sri Lankans would appear in court this week. The fate of the Chinese remains unclear, the BBC said.
The arrests likely will be handled with care because of increasing political and economic ties between Colombo and Beijing. China possibly is seeking a base in Sri Lanka for its growing navy.
Analysts say Sri Lanka in turn would benefit from an influx of Chinese money and expertise for infrastructure development, the BBC reported.
China also is in talks with Russia to ensure the safe return of Chinese fishermen detained off the coast of Vladivostok, in Russia's Far East region.
Last month Beijing announced that it had agreed to a procedure with Russia for discussing fishing issues including exchanges of fishing rights in their respective waters, Xinhua reported.
The meetings also would be a forum for settling "sudden and individual" cases of arrests of fishermen for suspected illegal fishing.
The agreement came while Chinese and Russian authorities discuss the release of the two Chinese fishing ships from China's eastern Shandong province, which were seized by the Russians.
Xinhua reported that a Russian coast guard vessel fired shots at one of the two.
A Chinese fisherman went missing after the boat he was aboard collided with a Russian ship that chased the Chinese one.
Vladivostok is near the southern tip of the Muravyov-Amursky Peninsula and close to Russia's border with China and North Korea. The city is home to the Russia's Pacific Fleet and the largest Russian port on the Pacific Ocean.
Fishing rights also have been an issue between China and its erstwhile ally North Korea.
In May North Korea released 28 Chinese fishermen after holding them for 13 days on suspicion of illegal fishing, Xinhua reported.
Detention of Chinese fishing ships and those from other countries on the South China Sea likely will continue to cause friction because of disputed ownership of many small islands and shoals.
The Philippines and China have been at loggerheads over the Scarborough Shoal whose rocky outcrops are claimed by Beijing and Manila.
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