Ocean Park on Monday said the two newborn pandas were doing well, but they remain fragile and it would probably take a few weeks before they started showing signs of strength.

Ocean Park chairman, Paulo Pong, said veterinary experts were working behind the scenes to help Ying Ying care for the cubs that were born last week.

He said on RTHK the park was thankful the Sichuan panda research centre had been providing the SAR with milk to feed the cubs, because Ying Ying doesn't have enough.

The mother gave birth on the eve of her 19th birthday – the human equivalent of being 57 years old. The delivery makes her the oldest known first-time panda mother.

Pong said the newborns have been eating and discharging well, and it would be another week or two before they grow black and white fur.

"Mainly I think the key is how the babies eat. How much breast milk they can take in, and that they can feel the temperature from their mother - how they sleep and rest. All these are important aspects for newborn pandas," he said.

"So now that we offer help artificially, on top of Ying Ying learning slowly how to care for the cubs, these things really complement each other. And we hope things will continue on smoothly."

Pong said it could take the newborns two months before they open their eyes, and learn how to walk some four months after birth. He said the theme park would try to give timely updates on the pandas, all while not giving too much pressure to the conservation experts.

He added the park would first discuss internally how it would expand its existing facilities to house six pandas, as Beijing's gift of two more are arriving next month.

There's time, Pong said, since it would take around two to three years for the cubs to leave Ying Ying and live on their own.