North Korea fired five short-range missiles into the East Sea on Monday in the latest of a series of provocations in response to the ongoing South Korea and U.S. joint military drills.

The missiles were launched near the northeastern city of Hamhung from 3:19 p.m. to 4:05 p.m. and flew east some 200 kilometers, according the Joint Chiefs of Staff (JCS).

The type of missiles fired was not immediately known.

"Our military is keeping close tabs on the situation and standing by with a heightened defense posture," the JCS said.

This is North Korea's third missile launch in less than two weeks.

Four days into the beginning of the joint military exercises on March 10, the North fired two Scud missiles into the East Sea.

On Friday, the country shot off another pair of mid-range ballistic missiles, but one of them reportedly blew up mid-flight.

Before and after Seoul and Washington kicked off their annual combined military exercises, Key Resolve and Foal Eagle, the North reacted with belligerent rhetoric, threatening nuclear attacks on both of the allies.

North Korea regards the joint exercises as a dress rehearsal for an invasion, although the allies say they are only defensive in nature. (Yonhap)