Emperor Naruhito plans to attend the state funeral of Queen Elizabeth II in Britain, Japanese government sources said Saturday.

Empress Masako, who has long battled a stress-induced illness, is also expected to attend the ceremony depending on her condition, the sources said. Prime Minister Fumio Kishida is also considering attending, according to TV Asahi.

Following the death of Queen Elizabeth at age 96 on Thursday, the imperial couple as well as former Emperor Akihito and former Empress Michiko began observing three days of mourning from Friday, the sources said.

The emperor traditionally does not attend funerals. Emperor Akihito became the first to do so when he and his wife traveled to Belgium for the funeral of King Baudouin in 1993.

Emperor Naruhito, who studied at Oxford University in the 1980s, on Friday praised the queen for her life of service, saying in a statement conveyed by the Imperial Household Agency, "I express my heartfelt sorrow and deep sadness."

"From my heart, I declare my gratitude and esteem for her many achievements and contributions," the emperor said in the message, in which he also recalled his warm meetings with the queen while he was studying at Oxford.

The emperor and empress had planned to visit Britain in 2020 for their first overseas trip following his accession to the throne in May 2019, but it was postponed due to the coronavirus pandemic.

Elizabeth, who visited Japan in 1975 to meet Emperor Hirohito, made a "great contribution" toward strengthening Japan's ties with Britain, Kishida said Friday.