Here are the top 10 updates on this big story
The Quad leaders, including Prime Minister Narendra Modi, US President Biden, Japanese Prime Minister Fumio Kishida and Australia's newly-elected Prime Minister Anthony Albanese, shared concerns over the situation in Ukraine.
They unveiled plans to invest at least $50 billion into infrastructure projects in the region over the next five years and a maritime monitoring initiative, which is expected to bolster surveillance of Chinese activities.
In his opening remarks earlier today, PM Modi said that the Quad has gained a significant place on the world stage in a short span of time, and it is moving ahead with a constructive agenda for the Indo-Pacific region which will further strengthen its image of a "force for good".
He noted that the Quad member countries have increased mutual coordination in several areas like vaccine delivery, climate action, supply change resilience, disaster management and economic cooperation. "Quad grouping has ensured peace, prosperity and stability in Indo-Pacific," he added.
US President Joe Biden said that Washington would stand with its "close domestic partners" to push for a free and open Indo-Pacific region. "Russia's assault of Ukraine only heightens the importance of those goals of fundamental principles of international order, territorial integrity and sovereignty," he said.
Japanese Prime Minister Kishida said that the Russian invasion of Ukraine has challenged the principles enshrined in the UN Charter. "We should never ever allow a similar incident to happen in the Indo-Pacific region," PM Kishida said.
Australia's Prime Minister Anthony Albanese also pledged more support for Pacific nations including aid to deepen "our defence and maritime cooperation".
PM Modi also held bilateral talks with President Biden on the sidelines of the summit. The two leaders discussed ways to strengthen cooperation in trade, investment, technology, defence, and people-to-people ties between the two countries.
The Summit in Tokyo is the fourth interaction of Quad Leaders. President Biden hosted the first-ever Quad summit in the virtual format in March last year, which was followed by an in-person summit in Washington in September. The Quad leaders also held a virtual meeting earlier this year in March.
In November 2017, India, Japan, the US and Australia gave shape to the long-pending proposal of setting up the Quad to develop a new strategy to keep the critical sea routes in the Indo-Pacific free of any influence.