North Korea fired an intermediate- or longer-range ballistic missile toward the East Sea on Thursday, South Korea's military said, following its continued refusal to answer what used to be daily cross-border calls.

The Joint Chiefs of Staff said it detected the launch in the vicinity of Pyongyang at 7:23 a.m. It did not elaborate further pending an analysis.

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

The North's last launch involving an intermediate-range ballistic missile or a longer-range one was that of a Hwasong-17 intercontinental ballistic missile on March 16.

This week's launch came amid speculation that the recalcitrant regime could fire a long-range rocket to put its first military satellite into orbit given its professed plan to finish preparations for the launch by this month.

Since last Friday, the North has not responded to routine cross-border calls through inter-Korean liaison and military communication lines, raising concerns that the absence of regular contact could lead to provocations by the reclusive regime.

Pyongyang has recently ratcheted up tensions through hardening rhetoric and other provocative moves, such as the testing of what it claimed to be underwater nuclear attack drones.

North Korean leader Kim Jong-un has called for expanding his country's war deterrence in a more "practical and offensive" manner, as he presided over a key ruling party meeting Monday, according to Pyongyang's state media.

During the meeting, Kim was seen pointing to an apparent military operational map featuring key targets in the South -- a scene that raised speculation that he might have planned drills or other provocative acts with the targets in mind.

The latest launch came two days ahead of the 111th birthday of the late Kim Il-sung, the North's national founder and current leader's grandfather. It is called the Day of the Sun.

On March 27, the North fired two short-range ballistic missiles. (Yonhap)