Japan announced the official start of Tokyo's cherry blossom season on Tuesday, 10 days earlier than usual and tied with a record early start seen only twice before.

In past years the country's meteorologists have linked the increasingly early blooms to climate change, and temperatures in Tokyo have been unseasonably mild in recent days.

Tokyo's official cherry bloom records go back 70 years and the delicate white-pink flowers have only appeared this early in 2021 and 2020, according to the weather agency.

Japan's sakura or cherry blossom season is feverishly anticipated by locals and visitors alike, and the announcement of the Tokyo season start was alerted by major news agencies and covered live on television.

The blooms are traditionally celebrated with hanami, or viewing parties, with picnics -- and sometimes boozy festivities -- organised beneath the trees.

But the public had been asked not to throw the parties during the pandemic, and the tourists that usually flood into the country for the season were kept out with strict border closures.

Borders reopened last October, and Tokyo parks have announced blossom revellers will be allowed to gather freely for the first time since 2019.

The season is announced underway based on the progress of blossoms on a signal tree at Tokyo's Yasukuni Shrine, where an official from the Japan Meteorological Agency stood before media and onlookers to make the announcement.

"Today, on March 14, we hereby declare the sakura blossoming in Tokyo," he said, in an announcement that came six days earlier than last year.

"We've seen many warm days in March," the official said, adding: "climate change may also have played a part."

The blooms of the ubiquitous somei-yoshino strain, which accounts for more than 90 percent of the cherry trees planted in Japan, last only around a week and tend to emerge simultaneously in a given region because the trees are clones of a single specimen.

"Congratulations on the blooming!", an onlooker shouted after the official announcement, to a round of enthusiastic applause.