The White House on Friday said North Korea recently provided Russia with a shipment of weapons, raising concerns about the expanded military relationship between the two countries.
The White House showed a series of satellite images that it said indicate cargo from an ammunition depot in North Korea (DPRK) was loaded on to a Russian-flagged ship and then taken by rail to a depot near Russia's southwestern border. The delivery took place between September 7 and October 1, the US said.
North Korean leader Kim Jong Un and Russian President Vladimir Putin met for a rare summit last month at which they discussed military matters, the war in Ukraine and possible Russian help for the secretive state's satellite programme.
In return for support, North Korea is seeking military assistance from Russia, including fighter aircraft, surface-to-air missiles, armoured vehicles and other advanced technologies, Kirby said.
The US is closely monitoring whether Moscow will deliver the weapons, but early signs of Russian ships offloading materials in North Korea may represent initial deliveries, he added.
The US said it will continue to enforce sanctions and make the case at the United Nations that the actions violate security council resolutions.
Israeli military strikes across Gaza killed at least 22 people on Wednesday, Palestinian medics said, as the US stepped up efforts to overcome sticking points between Israel and Hamas to reach a ceasefire to end the war.
At least 126 people have been killed by Tuesday's 6.8 earthquake in Tibet, while more than 400 people trapped in the foothills of the Himalayas have been rescued, and over 30,000 residents relocated, as the search for survivors continues.
A rapidly growing wildfire raged across an upscale section of Los Angeles on Tuesday, destroying homes and creating traffic jams as 30,000 people evacuated beneath huge plumes of smoke that covered much of the metropolitan area.
A magnitude 6.8 earthquake rocked the northern foothills of the Himalayas near one of Tibet's holiest cities on Tuesday, Chinese authorities said, killing at least 95 people and shaking buildings in neighbouring Nepal, Bhutan and India.