Taipei, Taiwan - A Chinese-crewed cargo ship was on Tuesday detained by Taiwanese authorities after a major underwater telecommunications cable was severed off the island.

Chunghwa Telecom reported the cable between Penghu, a strategic island group in the sensitive Taiwan Strait, and Taiwan was disconnected early on Tuesday, the Ministry of Digital Affairs said.

In response, Taiwan's Coast Guard intercepted the Togolese-registered ship Hongtai and escorted it back to Taiwan along with its crew.

According to the coast guard, the case was being "handled in accordance with national security-level principles."

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"Whether the cause of the undersea cable breakage was intentional sabotage or a simple accident remains to be clarified by further investigation."

The Hongtai, using a flag of convenience, was crewed by eight Chinese nationals and had Chinese funding, the coast guard claimed.

Flags of convenience allow shipping companies to register their vessels in countries to which they have no link.

Taiwan increasingly fears that China could sever its communication links as part of an attempt to seize or blockade the island, which it considers to be part of its soverign territory.

Over the last year, tensions have skyrocketed between Beijing and Taipei, with China conducting threatening military drills in surrounding waters.

"It cannot be ruled out that it was a grey zone intrusion by China," the coast guard said, referring to actions that fall short of an act of war.

"The coast guard will cooperate with the prosecutors in the investigation and make every effort to clarify the truth."