The UK's first state funeral in 57 years follows a strict protocol and will be steeped in military traditions, with rehearsals being undertaken for many days.
Ahead of Monday's funeral service, the President is invited to a reception hosted by King Charles and Queen Consort Camilla at Buckingham Palace.
A man has been arrested after running towards the coffin of Queen Elizabeth II, Lying-in-State at Westminster Hall in London as thousands of mourners file past to pay their respects.
"The incident is not being treated as terror-related," the Met Police said.
According to reports, the UK Foreign, Commonwealth and Development Office has invited Chinese President Xi Jinping as Head of State of a country with which the UK has diplomatic relations.
Queen Elizabeth II will be buried with her late husband Prince Philip at the conclusion of a solemn state funeral service made up of an hour-long ceremony at Westminster Abbey in London on Monday, Buckingham Palace announced on Thursday.
Members of the public began filing past at 5pm local time and will have until 6.30am on the day of the funeral, by which time several thousands are expected to have queued for hours to pay their respects to the Queen.
The UK capital on Wednesday unleashed a major operation to manage the several thousands of people expected to queue over the next few days to pay their respects to Queen Elizabeth II as she lies in state at Westminster Hall.
A ceremonial procession is scheduled for Wednesday afternoon that will see the coffin travel in a gun carriage from Buckingham Palace to the Palace of Westminster, or the Houses of Parliament building.
'We, too, smile knowing that you and grandpa are reunited now, and both together in peace'
Quoting Shakespeare, he noted: "As Shakespeare said of the earlier Queen Elizabeth, she was a pattern to all princes living."
Thousands lined the route to catch a glimpse as Queen Elizabeth II's coffin, seen in public for the first time, made its journey on Sunday from Balmoral Castle in Aberdeenshire to arrive at the late monarch's official Scottish residence of Holyroodhouse Palace in the capital city of Edinburgh.
Prior to the state funeral, the late British monarch will lie-in-state at Westminster Hall nearby for four days to allow the public to pay their respects.
In their first phone call since Truss assumed office earlier this week, Modi conveyed his condolences on the death of Queen Elizabeth II on behalf of all Indians and paid tribute to the 96-year-old late monarch's "lifetime of service".
"God save the King" were the words with which those gathered reaffirmed the proclamation made by the clerk of the council.
Charles will be formally proclaimed as King at the Accession Council at 10am local time on Saturday in the State Apartments of St. James's Palace, Buckingham Palace has said. It will mark the first time in history that the ceremony will be televised.
Churches also tolled their bells, after the Church of England sent out guidance to parishes, chapels and cathedrals across the country encouraging them to open for prayer or special services. Major sporting events, including football and cricket matches, have been postponed as a mark of respect.
King Charles III, Britain's new monarch who ascended to the throne on the death of his mother Queen Elizabeth II, has a strong connection with India and its age-old traditions of Yoga and Ayurveda.
Queen Elizabeth II, who died aged 96 on Thursday, was the first British monarch to accede to the throne after India's Independence from colonial rule in 1952 and admired the 'richness and diversity' of India where she made three State Visits over the course of her reign -- in 1961, 1983 and 1997.
"The Queen died peacefully at Balmoral this afternoon," Buckingham Palace announced in a statement on Thursday.