WASHINGTON -- The United States continues to work closely with South Korea to monitor threats posed by North Korea, a Pentagon spokesperson said Thursday, after a group of North Korean drones infiltrated South Korea before returning home.

Defense Department spokesperson Brig. Ge. Pat Ryder also highlighted that the US maintains "intelligence capabilities" in the region.

"We certainly have been very clear from here about the threats posed by the DPRK, as well as our commitment to working closely with the ROK, Japan and other partners in the region to uphold regional stability and security," Ryder said when asked about the drone incident.

"And so we will continue to coordinate closely with the South Korean government and (the) Ministry of Defense as those threats can continue to exist," he added.

DPRK stands for the Democratic People's Republic of Korea, the North's official name.

Five North Korean unmanned aerial vehicles crossed the inter-Korean border into South Korea last week in what Seoul has called a clear violation of the 2018 inter-Korean military agreement aimed at reducing cross-border tension.

Ryder declined to comment when asked if the US had detected North Korean drones in the past, but said the US maintains intelligence capabilities throughout the region.

"I am not going to go into specific intelligence about what we may or may not be tracking," he said. "Certainly, we have intelligence capabilities throughout the region, but I am not prepared to go into details."

The Pentagon spokesperson expressed concerns over North Korean leader Kim Jong-un's recent call at a party meeting to expand his country's nuclear arsenal exponentially.

"We continue to be concerned by the comments coming out of North Korea, and again, it just demonstrates the destabilizing impact that these kinds of comments and the actions have," said Ryder.

He also reiterated the US' commitment to engage in dialogue with Pyongyang.

"We are open to discussions and communication with North Korea, with no strings attached," said Ryder.

"But at this point and time, North Korea has chosen to not do so. And so we will continue to work very closely to try to ensure the safety and security and stability of the Indo Pacific region," he added. (Yonhap)