China has demanded that Russia release Chinese fishermen and boats detained earlier this week, state media reported.
Vice Foreign Minister Cheng Guoping expressed "strong dissatisfaction" over the matter in a statement late Thursday when summoning a Russian diplomat, the official Xinhua news agency reported.
A statement on the website of China's consulate in the eastern Russian city of Khabarovsk said the sailors from one ship were being held for fishing illegally and were taken to the eastern port of Nakhodka for "investigation".
The consulate quoted Russian media as saying that the coastguard discovered the Chinese vessel in Russian waters on Tuesday, and fired weapons after encountering resistance from the Chinese crew, though no one was reported to be injured.
Xinhua also said a second Chinese fishing vessel carrying 19 sailors had been seized. Both ships were from Weihai in the eastern province of Shandong.
Cheng demanded that Russia carry out a thorough investigation and release the sailors quickly, Xinhua said.
According to Xinhua, the Russian diplomat said officials were investigating and would inform China as quickly as possible.
Xinhua quoted the Chinese consulate in Vladivostok as saying that the ships were seized for allegedly entering Russia's exclusive economic zone.
Such maritime disputes between China and Russia are rare. Ties between them have strengthened as the neighbours, which are both permanent members of the UN Security Council, have sought to block Western-backed action on Iran and Syria.