Washington, Mar 26 (IANS): The US will "respond" to North Korea if it continues to escalate tensions by testing ballistic missiles, President Joe Biden said on Thursday.

"We're consulting with our allies and partners, and there will be responses if they choose to escalate. We will respond accordingly," Biden told reporters, DPA news agency reported.

In the early hours of Thursday North Korea test-fired its first ballistic missiles since Biden took office, in a show of force to the new administration in Washington.

Two short-range missiles were fired from the North Korean town of Hamju and travelled some 450 km at an altitude of 60 kilometres, the South Korean military's Joint Chiefs of Staff (JCS) said.

Biden said he was "prepared for some form of diplomacy," but that the dialogue must be preconditioned upon "the end result of denuclearization."

When asked by a reporter if North Korea was his "top foreign policy issue," Biden responded: "Yes."

The test-fires had triggered prompt condemnation from Japan, one of Washington's closest allies in region.

Japanese Prime Minister Yoshihide Suga said Tokyo is making "a serious protest" after Pyongyang fired the missiles into the Sea of Japan - known in South Korea as the East Sea - and that Tokyo "strongly condemns" the act.

"The launch threatens the peace and stability of our country and the region and it was a clear violation of United Nations Security Council resolutions," Suga told reporters.

Russia's Foreign Minister Sergei Lavrov called for fresh negotiations over the peace process on the Korean peninsula.

During a visit to Seoul, Lavrov called for talks to find a solution to the problems on the divided peninsula. Russia is committed to peace and stability, he said.

It marks the second time Pyongyang has launched missiles in the past week.

North Korea fired two cruise missiles off its west coast on Sunday, Yonhap news reported on Wednesday.

That test on Sunday came in the wake of joint military exercises by the armed forces of South Korea and the US. The nine-day command exercise, which did not include field training, ended on Thursday last week.

The influential sister of North Korean leader Kim Jong Un, Kim Yo Jong, had condemned the military exercises and accused the new US administration of wanting to cause trouble as a first step.

North Korea is banned from testing ballistic missiles by UN resolutions, and has been slapped with tough international sanctions to deter it from continuing to develop rockets that could be equipped with nuclear warheads.