During talks in the Japanese city of Hiroshima, the leaders vowed: "to stand together against Russia's illegal, unjustifiable, and unprovoked war of aggression against Ukraine."
In a joint statement, the G7 nations said they were "imposing further sanctions and measures to increase the costs to Russia and those who are supporting its war effort" in order to "starve Russia's war machine."
"We are also building on the success of our efforts to ensure that Russia is no longer able to weaponize the availability of energy against us and against the world," the statement added.
G7 leaders called again for Russia to withdraw its troops from Ukraine and vowed more financial, humanitarian, military and diplomatic support to Kyiv "for as long as it takes."
DW's Chief International Editor Richard Walker, who is in Hiroshima, said G7 leaders were unequivocal in their backing for Ukraine.
"Overall, the message coming from the G7 on Ukraine is more of the same ... more support as it moves towards its highly anticipated counteroffensive and also to tighten the screws further on Russia," he said.
"They also want to reinforce the message that ...Ukraine must set the agenda of any peace talks. They don't want Russians to be in any position to dictate the terms."
G7 leaders summit kicks off in Hiroshima
Fresh US sanctions on Russia
The US component of the new sanctions will include cutting off about 70 companies from Russia and other countries from US exports, according to an unnamed US official cited by multiple media outlets.
The official added that 300 sanctions against individuals, entities, vessels and aircraft would be announced by G7 leaders.
"These will go after circumvention. These will go out for financial facilitators, as well as future energy and extractive capabilities of Russia and other actors helping to support the war," the official added.
Speaking ahead of the talks, German Chancellor Olaf Scholz said Berlin wanted pragmatic measures to prevent the circumvention of sanctions imposed on Russia.
The US has so far frozen Russian Central Bank funds, restricted banks' access to SWIFT — the dominant system for global financial transactions — and sanctioned thousands of Russian firms, government officials, oligarchs and their families.
Last year, G7 nations collectively imposed a $60 per-barrel price cap on Russian oil and diesel.
UK to bank Russian diamonds
On Twitter, UK Prime Minister Rishi Sunak announced a ban on Russian diamonds and imports of metals from Russia, including copper, aluminum and nickel.
Britain will also target an additional 86 individuals and companies involved in Russian President Vladimir Putin's "military-industrial complex," Sunak's government said, in addition to those involved in energy, metals and shipping industries.
The G7 as a whole is expected to further announce restrictions on the multi-billion dollar export of rough diamonds from Russia.
European Council President Charles Michel also said on Friday that the bloc wants to limit trade in Russian diamonds.
Zelenskyy to attend G7 summit in person — official
"Very important things will be decided there and therefore the presence of our president is absolutely essential in order to defend our interests," Oleksiy Danilov, secretary of the National Security and Defence Council, told state television.
However, there has been no formal announcement by Zelenskyy's office.
Zelenskyy arrived in Saudi Arabia for the Arab League and was later expected to head to Japan on a French government plane, according to reports.
Ahead of his talks with Chancellor Olaf Scholz last Sunday, Germany announced a new military aid commitment worth €2.7 billion ($2.91 billion) to Ukraine.
DW's Richard Walker said Zelenskyy will get a chance to address Asian leaders who are also attending the summit:
"The opportunity to potentially get face time with [Indian Prime Minister] Narendra Modi and other leaders who have remained on the fence so far [over Russia's invasion of Ukraine] is particularly interesting for Zelenskyy."
Indian TV channels later reported that Modi was due to meet the Ukrainian president on the sidelines of the talks.
US will back training Ukrainian pilots on F-16s — reports
US President Joe Biden will allow Ukrainian pilots to be trained on American F-16 fighter jets, a senior US government official said. A decision on the delivery of fighter jets to Ukraine is to follow at a later date, according to the official.
Biden told the other G7 leaders the United States would support the training of Ukrainian pilots on fourth-generation fighter jets, including the F-16, the official said.
While the training is ongoing, the coalition of countries participating in the effort will decide when to provide jets, how many to provide and who would provide them, he said. The training will take place outside Ukraine at sites in Europe and would run for several months, he said. Training would start in the coming weeks.
Ukraine has been calling for the US-made jets for some time, saying they would be more effective than the Soviet-era jets it currently has. Western countries have often said a prerequisite for any deliveries would be first training Ukrainian pilots to operate them. Some such initiatives are already in the works.
Some other NATO members have already begun training Ukrainian pilots, but US involvement in such schemes could be a positive sign for Kyiv's hopes.
Tokyo calls for nuclear disarmament
The first stop on Friday for world leaders, including US President Joe Biden, was a wreath-laying ceremony at Hiroshima's cenotaph, where Japanese Prime Minister Fumio Kishida called for a world free of nuclear weapons. Kishida said the achievement would be his life's work.
The US dropped a nuclear bomb on Hiroshima on August 6, 1945, to force a quick Japanese surrender in World War II. An estimated 140,000 people were killed.
Some 78 years later, the nuclear threat remains elevated.