U.S. Secretary of Defence Lloyd Austin speaks during a Ukraine Defence Contact Group meeting at the U.S. air base in Ramstein, Germany, Sept. 6. AFP-Yonhap

The defense chiefs of South Korea and the United States reiterated the "robustness" of the two countries' alliance in a phone call Thursday, the Pentagon said, as Pyongyang has ratcheted up tensions with missile launches and other provocative moves.

Seoul's Defense Minister Kim Yong-hyun and U.S. Defense Secretary Lloyd Austin held the talks after Pyongyang launched multiple short-range ballistic missiles into the East Sea and unveiled a new road-mobile missile launcher earlier this week.

"The two leaders reviewed the security situation on the Korean Peninsula and in the region," Pentagon press secretary Maj. Gen. Pat Ryder said in a readout.

"Both officials reaffirmed the robustness of the ROK-U.S. Alliance and reviewed priorities to strengthen the combined defense posture," he added, referring to South Korea by its official name, the Republic of Korea.

Austin also noted that he looked forward to hosting Kim for the allies' annual defense ministerial talks, called the Security Consultative Meeting, which is slated to take place in Washington later this year.

This week, Pyongyang has been raising tensions on the Korean Peninsula.

On Friday (Korea time), the North's state media revealed that North Korean leader Kim Jong-un recently visited a uranium enrichment base — a rare disclosure of Kim's tour of such a key nuclear site. There, he called for increasing the number of centrifuges for uranium enrichment.

The move and other provocative acts came amid lingering concerns that Pyongyang could engage in major provocations near the U.S. presidential election, possibly to bolster its leverage. (Yonhap)