(CNN) -- A South Korean fishing boat in the Sea of Japan and its seven crew members are being held by North Korea, according to reports in South Korea.
North Korean state media is reporting that the crew was "detained."
There are few details which have emerged from the incident; but it comes amid mounting tensions following the March sinking of a South Korean warship. Forty-six sailors died, and South Korea blamed it on a North Korean submarine attack. The North calls the accusation "a fabrication."
The incident comes after South Korea's military carried out five days of military exercises in the Yellow Sea. The South Korean navy, army, air force and marines are practicing techniques for detecting and evading North Korean submarines and guided missiles, South Korea's Yonhap news agency reported Saturday. The exercise involved 20 ships and 4,500 troops, according to Yonhap.
North Korea said Friday it would "react with strong physical retaliation to the anti-submarine drill to be staged by the group of traitors in the West Sea," according to the official Korean Central News Agency.
"Our warnings are not empty rhetoric," said Rodong Sinmun, the newspaper of the North's ruling Workers' Party, according to Yonhap.