South Korea fires warning shots after boats from North cross sea border

North Korean leader Kim Jong Un attends the first congress of the country's ruling Workers' Party in 36 years, in Pyongyang, North Korea, in this photo taken by Kyodo May 9, 2016. Mandatory credit Kyodo/via REUTERS

SEOUL (Reuters) - North Korea threatened retaliation on Friday after South Korea fired what it said were warning shots when a patrol boat and fishing boat from the North crossed the disputed sea border off the west coast of the Korean peninsula.

The two vessels from the North retreated about eight minutes after the South Korean navy fired five 40 mm artillery shots at around 7:30 a.m. local time, South Korean officials told Reuters.