Russia earlier this year provided satellite data to help Yemen's Houthi rebels strike ships in the Red Sea, the Wall Street Journal alleged on Thursday.
The US daily -- citing "a person familiar with the matter" and two anonymous European defense officials -- reported that the data was transmitted by Iranian intermediaries and used to target ships with missiles and drones.
The Houthis, who control vast swaths of Yemen, started targeting commercial shipping in the Red Sea in what they say is solidarity with Palestinians after Israel began its war on Gaza.
The attacks have led to a dramatic drop in traffic through the key shipping lane.
In response, the United States and Britain deployed a naval coalition to the region and have bombed Houthi targets in Yemen.
In more than 100 Houthi attacks over nearly a year, four sailors have been killed and two ships have sunk, while one vessel and its crew remain detained since being hijacked last November.
Russian leader Vladimir Putin has been keen to push back against the political and economic isolation imposed on his country by the West since his invasion of Ukraine in 2022.
The report in the Journal comes on the heels of a summit of the BRICS countries, a diplomatic grouping that draws together nine countries that account for almost half the world's population, including China, India and Iran.
Separately, Moscow faced fresh accusations of escalating the conflict in Ukraine this week with the United States, South Korea, NATO and Kyiv all saying North Korea had sent troops to Russia.