The death of a baby panda in Japan stopped regular television programming and brought a Tokyo zoo director to tears Wednesday, a week after its birth sent ripples of excitement across the nation.

Newscasts had dedicated a nightly segment to the male cub's daily activities since his birth on July 5, with retailers unveiling a host of panda-themed products in celebration.

The unnamed cub was initially hailed as a rare success for Japan's captive breeding programme as it was the zoo's first panda born in 24 years and the only one conceived from natural sexual intercourse.

But the enthusiasm turned to grief on Wednesday after Ueno zoo in the Japanese capital said the tiny, 144-gram male infant had died of pneumonia, bringing zoo director Toshimitsu Doi to tears.

"We are very disappointed," Doi said as he wiped his eyes.

Newscasters interrupted regular programming to report the death of the cub, whose birth had been embraced as happy news for a country still struggling to recover from last year's quake-tsunami disaster.

Prime Minister Yoshihiko Noda described the death as "very disappointing".

"We were all looking forward" to the cub's development, he told reporters in Tokyo.

Matsuzakaya, a major Japanese department store, had planned a "Happy Panda Week" celebration, offering special discounts following the birth, but the event was canceled on Wednesday.

The zoo said keepers found the baby lying on its back against its mother Shin Shin's stomach.

"They administered a cardiac massage and other treatment, but unfortunately they confirmed its death at 8:30 am (2330 GMT Tuesday)," the zoo said.

Shin Shin and her mate Ri Ri were leased from China last year at an annual cost of about one million dollars to the zoo operated by the Tokyo Metropolitan government.

The baby was hailed in China, which has sometimes hostile relations with neighbouring Japan.

"We lament the loss of the cub and believe that the Japanese people, who have been looking forward to seeing the cub, will also lament this loss," said foreign ministry spokesman Liu Weimin in a statement Wednesday.

Last week Beijing expressed hope "people-to-people sentiment and overall relations between China and Japan" could be promoted by the cub's birth.

China is famed for its "panda diplomacy", using the bears as diplomatic gifts to other countries. About 1,600 remain in the wild in China, with some 300 others in captivity worldwide -- mostly in China.

As many as 16 giant pandas have been born in Japan, according to reports.