SEOUL, South Korea (AP) - South Korea's Red Cross pressed North Korea on Wednesday to release a boat and its seven-man crew seized off the east coast last weekend while Seoul was carrying out large-scale, anti-submarine naval drills.
Relations between the two Koreas have been tense since the deadly sinking of a South Korean warship in late March that Seoul and the United States blame on North Korea.
In response, South Korea and the U.S. have launched a series of military drills in the waters off the Korean coast in recent weeks, drawing a barrage of artillery fire from North Korean troops stationed on the coast on Monday.
The firing of more than 100 rounds of artillery into the sea, some of which landed in South Korean waters, complicated prospects for the quick return of the four South Koreans and three Chinese and their fishing boat, seized Sunday.
Pyongyang said the boat illegally entered the waters of North Korea's exclusive economic zone, according to South Korea's coast guard.
On Wednesday, South Korea's Red Cross demanded their swift release in a call to its North Korean counterpart via a military hot line, officials said.
"The Red Cross called on North Korea to immediately repatriate our vessel and fishermen in line with an international law and practice and on humanitarian grounds," Unification Ministry spokeswoman Lee Jong-joo told reporters in Seoul.
North Korea didn't immediately respond to the request, Unification Ministry and Red Cross officials said.
It is not unusual for North Korea to detain foreigners accused of border violations.
Last year, North Korea freed four South Korean fishermen after detaining them for a month for illegally entering North Korean waters. The North also has been holding an American since January for entering the country illegally and committing an unspecified "hostile act."
North Korea fired about 110 rounds from its western shores late Monday afternoon - just minutes after the South Korean military concluded five days of large-scale naval drills staged in response to the sinking of the Cheonan warship, which killed 46 sailors.
Most of the shells landed in North Korean waters, but about 10 reached South Korean waters not far from an island inhabited by fishing families and South Korean troops. No damage was reported, but Seoul's Defense Ministry denounced the firing as a grave provocation and violation of their cease-fire, and warned it would deal "sternly" with any more aggression.
The two Koreas technically remain in a state of war because the 1950-53 Korean War ended with an armistice, not a peace treaty. The U.S. stations about 28,500 soldiers in South Korea to protect the longtime ally.