North Korea seizes South Korean fishing boat. How long will it hold the crew?

North Korea has seized a South Korean fishing boat that may have intruded accidentally into the North’s exclusive economic zone off the east coast of the Korean peninsula, South Korea’s Coast Guard said Sunday.

North Korea has seized numerous South Korean vessels over the years, but this incident comes during South Korean naval exercises in the Yellow Sea. North Korea has denounced the exercises as a “provocation” and threatened to answer “fire with fire.” A South Korean admiral has said South Koreans will “immediately counterattack” if fired on.

The question is how long North Korean authorities will hold the four South Korean members of the crew of the fishing boat while tensions are high surrounding the exercises. The crew also includes three Chinese whom North Korea is expected to release in view of the North’s close ties with China.

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“It complicates things for North Korea for the crew to include Chinese and South Koreans,” said Mingi Hyun, a research fellow at the Korea Institute for Maritime Strategy. “They’re going to have to treat them equally.”

Nonetheless, he said, “If the boat did cross into North Korea’s exclusive economic zone, that’s reason to hold them.”

A South Korean Coast Guard official said one of the members of the crew had been able to respond to a call by satellite phone while the boat was still under tow by a North Korean patrol boat. He had said “yes” when asked if the boat was on the way to a North Korean port, according to Yonhap, the South Korean news agency.

While South Korean officials were trying to determine the fate of the seven-man crew on the fishing boat, South Korean vessels conducted nighttime live-fire antisubmarine exercises. The exercises are in the same general area where a South Korean Navy corvette, the Cheonan, was sunk on March 26, killing 46 members of its 104-man crew. An South Korean investigation that included experts from five foreign countries found that a North Korean midget submarine fired a torpedo the split the Cheonan in two.

South Korean vessels, supported by warplanes, began firing on targets in the Yellow Sea at sundown and were expected to keep up the exercises for the next six or seven hours. The exercises are near the disputed “northern limit line” below which North Korean vessels, including fishing boats, are banned.

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North Korea has challenged the validity of the line, provoking bloody battles in 1999 and 2002 and an episode in November of last year in which a South Korean corvette poured fire onto a North Korean patrol boat, sending it back to port in flames. The sinking of the Cheonan was believed to be in revenge for that humiliation.

A South Korean defense official said the reason for the naval drill “is to improve the military’s capabilities to detect North Korean submarines and torpedoes.” The idea, he said, was to stage the drill when there was no moon over the sea.

Yonhap quoted him as saying “the ongoing no-moonlight period seems to have added to the effectiveness of the large-scale training.”