Russia has allowed the release of millions of dollars in frozen North Korean assets and may be helping its isolated ally with access to international banking networks, assistance that has come after the North’s transfer of weapons to Moscow for use against Ukraine, according to American-allied intelligence officials.

The White House said last month that it had evidence that North Korea had provided ballistic missiles to Russia, and that the North was seeking military hardware in return. Pyongyang also appears to have shipped up to 2.5 million rounds of ammunition, according to an analysis by a British security think tank.

While it is unclear whether Russia has given North Korea the military technology it may want, new banking ties would be another sign of the steady advancement in relations between the two countries. The expanding partnership has most likely emboldened the North, as it has issued a stream of belligerent threats in recent months, U.S. officials say.

Russia has allowed the release of $9 million out of $30 million in frozen North Korean assets deposited in a Russian financial institution, according to the intelligence officials, money that they say the impoverished North will use to buy crude oil.

In addition, a North Korean front company recently opened an account at another Russian bank, the intelligence officials say, evidence that Moscow may be helping Pyongyang get around U.N. sanctions that prohibit most banks from doing business with North Korea. Those sanctions have choked the North’s economy and largely shut the country off from international financial networks.

The new bank account is held in South Ossetia, a self-proclaimed independent state in the Caucasus region that has close connections with Russia, according to the officials, who spoke on the condition of anonymity to discuss sensitive intelligence matters.