The fishermen arrived at China's northern port city of Dalian and immediately were sent to a local hospital for checkups, Xinhua said.
Most reported being exhausted but otherwise appeared in good shape, a hospital spokesmen said.
Their release ends nearly two weeks of diplomatic negotiations about which few details emerged in either country's media, including whether it was North Korean maritime officials that detained the Chinese fishermen.
China's foreign ministry was reportedly in talks with North Korean officials concerning reports that fishermen were being held hostage by a group demanding around $190,000 for their release.
There was no indication that the fishermen had been detained for fishing illegally in North Korean waters.
One of the released fishermen told Xinhua that he was certain his vessel and the other vessels were in Chinese waters when they were picked up.
"We were detained at around 1 p.m. on May 8 when our boats were sailing and trawling in Chinese waters," he said.
"I still remember the coordinates of my boat at 123 degrees, 16 minutes east longitude and 38 degrees, 18 minutes north latitude," said Han Qiang, the skipper of one of the three detained boats.
Maritime territorial and illegal fishing disputes between China and North Korea -- staunch allies -- are few compared with China's clashes with its other maritime neighbors on the edges of the South China Sea.
Beijing and Manila remain in disagreement over ownership of the Scarborough Shoal, off the Philippines coast and where several Chinese fishing vessels remain after being detained by Philippines authorities.
The shoal is more than 400 miles off the Chinese coast but 150 miles off the coast of Zambales, a province on the western shore of Luzon Island, the largest and most northern Philippines island.
China's claim to Huangyan Island, as Scarborough Shoal is known in China, rests on interpretations of several treaties beginning with the Treaty of Paris 1898.
What makes ownership of Scarborough Shoal important -- as with the other disputed territories in the South China Sea -- is access to natural resources including oil and gas on the seabed and fishing rights in the area.
China insists on bilateral talks -- as it does with other disputes it has in the South China Sea -- to settle ownership of the shoal but the Philippines wants an international tribunal to rule on the matter.
This week Philippines Foreign Affairs Secretary Albert del Rosario will attend a high-level U.N. meeting in New York on the role of U.N. states in mediation, a report in the Manila Times said.
Del Rosario also will call on the Association of Southeast Asian Nations, various U.N. groups and the international community in general to mediate between Manila and Beijing over the row.
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