North Korea has test fired two short-range missiles into the East Sea.

A senior government official said Wednesday that the North fired two short-range missiles into waters off its eastern coast late Tuesday, shortly after launching two other short-range missiles earlier in the day. The North also fired three missiles on Monday, or the same day it conducted its second nuclear test.

The official said intelligence authorities are closely monitoring the situation.

Meanwhile, the military is strengthening its guard amid signs that the North could seek to launch missiles off its western coast. North Korea has banned vessels from its territorial waters along its northwestern coast until Wednesday evening.

Tensions between the two Koreas usually run high along the Northern Limit Line at this time of the year, as the two sides heighten their monitoring of Chinese fishing boats that flock into the area during the crab season, which lasts until next month.

The Northern Limit Line is a disputed maritime demarcation line in the Yellow Sea between the two Koreas.