Taipei, Taiwan - Taiwan said Sunday it had detained a Chinese boat suspected of illegally supplying fuel to fishing boats trespassing in Taiwanese waters, the coast guard said.

The incident happened on Sunday off the northwest coast near the cities of Taoyuan and Hsinchu, south of the capital Taipei, the coast guard said.

The boat ignored repeated warnings and "zigzagged to flee before it was brought under control".

"The boat was an unregistered Chinese refueling boat with its name painted over," operating in Taiwan's restricted waters, the coast guard said. "It had no name, no registered home port, and no ship certificate."

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The coast guard said It was carrying around 500,000 liters of fuel and had attempted to supply fuel to other Chinese vessels unlawfully entering Taiwanese waters.

The six crew members on board were "Chinese nationals with no identification documents", the coast guard said.

The boat was escorted back to port near Taipei, and the crew members were taken in for questioning.

Illegal fishing by Chinese boats has been a recurring concern for Taiwan, which has stepped up patrols to deter unauthorized boats and activities.

China claims self-ruled Taiwan as its own territory and has never renounced the use of force to bring the island under its control.

A series of incidents involving boats from both sides have fuelled tensions across the narrow waterway.

In February, Taiwan ordered a Chinese cargo ship captain to be detained for severing an undersea telecoms cable off the island.