South Korea strengthened the deployment of a controversial US-made missile defense system and launched a huge show of military might on Monday in response to North Korea's test of what it claimed to be a hydrogen bomb.
Seoul said the North appeared to be preparing to launch more missiles after Sunday's test rocked the region. South Korea conducted a series of live-fire drills and said the US was preparing to bolster its military presence.
Russia warned that it would consider ramping up its military assets in response, and China warned that the deployment of the missile defense system,THAAD, risked escalating the already tense situation.
The deepening crisis has caused frayed relations on both sides. North Korea's continued belligerence was a blow to China, which has failed to keep its ally in check despite persistent warnings. China said Monday it had made a "stern representation" to North Korea over the test.
Meanwhile Donald Trump, the US president, opened up a rift with South Korea, saying it risked "appeasement" of Pyongyang.