Moscow: After combined patrolling of the Pacific Ocean with Chinese warships for more than three weeks, manoeuvres that came close to the US West Coast, the Russian Navy ships have returned, Al Jazeera reported.

On Sunday, Al Jazeera reported citing Interfax news agency, that warships from the Russian Pacific Fleet crossed more than 7,000 nautical miles (13,000 km) through the Sea of Japan, the Sea of Okhotsk, the Bering Sea, and the Pacific Ocean.

A region known in Russia as the Kurils and in Japan as the Northern Territories, which has been the source of decades of tension between the neighbours, was traversed by the Russian-Chinese detachment during the patrol as it travelled along the northern Japanese island of Hokkaido.

A part of the Aleutian Islands archipelago was also surrounded by Russian and Chinese warships.

The Commander Islands, which are close to the Kamchatka Peninsula, are a part of Russia, but the majority of the Aleutian Islands are owned by the US state of Alaska.

In what looked to be the largest such flotilla to approach US coastlines, 11 Russian and Chinese ships travelled near to the Aleutian Islands, according to a Wall Street Journal report from early August.

According to the newspaper, which cited US officials, the ships never sailed into US territorial waters.

Al Jazeera reported, citing Interfax, that the exercise included some of the largest warships from the Russian Pacific Fleet.

“During the patrol, joint anti-submarine and anti-aircraft exercises were carried out. A search was made for submarines of a mock enemy using helicopters and aircraft of naval aviation from both sides. Mock missile firing was carried out at a detachment of mock enemy ships,” the news agency said.

China participated in a massive joint exercise with Russia in September that involved almost 2,000 personnel, 300 military vehicles, 21 combat planes, and three vessels.

According to the Russian defence ministry, the Vostok 2022 (East 2022) exercise included more than 50,000 soldiers and 5,000 weaponry units, including 140 planes and 60 warships. It was conducted at numerous sites in Russia's Far East and the Sea of Japan, Al Jazeera reported.