Khan, who arrived in Amritsar on Tuesday, paid a rich tribute to those who died in Jallianwala Bagh incident.
"It was incredibly moving to visit Jallianwala Bagh. Our thoughts are with all those who died.
"It is time for the British government to finally apologise. The tragedy in 1919 on the eve of Vaisakhi is one we must never forget," Khan wrote in the visitors' book at the Jallianwala Bagh here.
The massacre took place on April 13, 1919 when British troops commanded by Brigadier-General Reginald Dyer, opened fire at a crowd of unarmed people, on the harvest festival of Baisakhi.
A large number of people died in the incident.
The former British Prime Minister David Cameron, during his 2013 visit to Jallianwala Bagh, also condemned the tragedy and described it as a "deeply shameful incident" in British history. However, he stopped short of making any official apology.
Wrapping up his first official tour to India, the London Mayor, earlier today, also paid obeisance at the holy shrine of Golden Temple.
During his visit, he participated in langar at the Golden Temple complex and showed keen interest in knowing how the food is prepared.
Khan was also presented with a Siropa (robe of honour) by officials of the Shiromani Gurdwara Parbandhak Committee (SGPC).
"It has been a privilege for me to be in Amritsar for the last 24 hours. The Golden Temple is a spiritual home for tens of thousands of Londoners of the Sikh faith and millions of Sikhs around the world come to Amritsar to pay their respects to worship," he said while talking to the reporters.
Also, sharing the same sentiments on the visitors' book of the Golden Temple, he wrote: " The warmth, hospitality , spirituality are a lesson to us all. Thank you for providing me with memories that will stay with me forever".
On Tuesday evening, Punjab Chief Minister Amarinder Singh hosted a dinner for the London Mayor in Amritsar.
Khan, who was on a three-city tour to India, visited New Delhi, Mumbai and Amritsar to strengthen the UK's capital trade ties with India.
(This story has not been edited by Business Standard staff and is auto-generated from a syndicated feed.)