Seoul, Oct 1 (TIWN) North Korea fired two short-range ballistic missiles into the East Sea on Saturday, in its fourth such provocation in less than a week, South Korea's military said.

"While strengthening our monitoring and vigilance, our military is maintaining a full readiness posture in close cooperation with the US," the JCS said in a text message sent to reporters.

The latest launches followed earlier provocations on Sunday, Wednesday and Thursday. South Korea, the US and Japan staged an anti-submarine warfare (ASW) exercise in international waters of the East Sea on Friday.

The three countries have been reinforcing bilateral and trilateral security coordination amid concerns that the North could ratchet up tensions by conducting a nuclear test or other provocative acts.

On Thursday, US Vice President Kamala Harris made a daylong visit to South Korea, during which she met with President Yoon Suk-yeol and toured the Demilitarized Zone (DMZ) that divides Korea. While here, she said Washington would do "everything" in our power to ensure its security commitment to the Asian ally.