"The strength of the solidarity between the G7 foreign ministers is at a level not seen before," Japan's Foreign Minister Yoshimasa Hayashi told a news conference on Tuesday after hosting a meeting of the group in the Japanese resort town of Karuizawa.
The show of unity comes after French President Emmanuel Macron this month said the European Union should reduce its dependency on the United States and cautioned against being drawn into a Taiwan crisis.
Beijing, which views Taiwan as Chinese territory and has not renounced the use of force to take the democratically governed island, rebuffed the G7 comments as gross interference in its internal affairs, however.
The G7 communique highlights how the dual issues of Russian military intervention and fears of similar action by China against Taiwan have been a focus of the three-day meeting.
The group, which comprises the United States, Japan, Germany, Britain, France, Italy and Canada, described Russia's threat to put nuclear weapons in Belarus as "unacceptable". It said "any use of chemical, biological or nuclear weapons in Ukraine "would be met with severe consequences."
Russian President Vladimir Putin last month said Russia would station shorter-range, so-called tactical nuclear weapons because the NATO military alliance was expanding towards Russia's borders.
It was the first time since the Cold War ended three decades ago that Russia has suggested stationing nuclear forces in another country, raising the stakes in its intensifying stand-off with the West over Ukraine.
In a bid to limit Moscow's ability to wage its war, the G7 ministers in their communique also warned other nations, which the U.S. and other Western nation worry could include China, not to supply Russia's armed forces.
"We will reinforce our coordination to prevent and respond to third parties supplying weapons to Russia," they said.
US Secretary of State Antony Blinken last month said China had not yet supplied Russia with lethal aid, but US officials are also concerned about dual-use products, such as electronics components that can be used in missiles and other weapons.
In a news conference after the G7 meeting, Blinken criticised Russia after a days-long pause in the inspection of ships moving grains from Ukraine under a UN-brokered initiative.
On Tuesday Russian media said inspections had restarted.
Taking direct aim at China, the ministers also agreed that peace and security in the Taiwan Strait were critical and opposed militarisation of the South China Sea. They called on Beijing to act.
"We remind China of the need to uphold the purposes and principles of the UN Charter and abstain from threats, coercion intimidation and the use of force," the ministers said in the document, which included a condemnation of North Korea's missile launches and expressed concern about Myanmar, Afghanistan and Iran.
China's foreign ministry spokesperson Wang Wenbin said the G7 communique grossly interfered in the country's internal affairs, and maliciously smeared and discredited it.
The statements were "full of arrogance, prejudice against China," Wang told a regular media briefing, adding, "We have made a strong demarche to the host Japan."
Wang urged the G7 instead "to reflect on their own problems".
"We should abandon the Cold War mentality and ideological prejudices, stop condescending and pointing fingers at other countries, and stop artificially creating confrontation and division in the international community," he said.
