Cameron marks 1919 Amritsar massacre by British troops in India

New Delhi (CNN) -- UK Prime Minister David Cameron visited the site of the infamous 1919 Amritsar massacre by British troops in India on Wednesday -- but those hoping he might apologize for the atrocity were disappointed.

Cameron, the first serving British prime minister to visit Amritsar, a Sikh holy city in the northwestern state of Punjab, laid a wreath at a memorial to the hundreds killed in the massacre.

Writing in a book of condolences at the Jallianwala Bagh memorial, he described the massacre as "a deeply shameful event in British history." He added, "We must never forget what happened here."

However, he did not give a formal apology for the atrocity, which occurred while India was part of the British Empire.

 Cameron's remarks in the visitor book

Cameron's remarks in the visitor book

A spokesman for Cameron said the British state had always described the massacre as monstrous, but that "we need to be careful about going around apologizing for things that happened 40 years before the prime minister was born."

Cameron's trip to India is focused on promoting closer trade and business links.

Queen Elizabeth II and her husband, Prince Philip, previously visited Amritsar in 1997.

In 1920, then-cabinet minister Winston Churchill condemned the massacre as "an episode which appears to me to be without precedent or parallel in the modern history of the British Empire ... It is an extraordinary event, a monstrous event, an event which stands in singular and sinister isolation."

The atrocity occurred when a British Army general ordered troops to open fire to disperse a crowd of unarmed protesters who had gathered in Jallianwala Bagh, Amritsar.

A report by a British-led committee in the wake of the massacre put the number killed at close to 400, with three to four times as many people injured. Indian observers put the number killed at more than 1,000.