Berlin's main zoo has released new photos of twin panda cubs born this summer, saying the two are developing well.

The zoo said Thursday that the two cubs each now weigh about 5 kilograms (11 pounds) -- quite an increase from their 186 gram (6.56 ounce) and 136 gram (4.8 ounce) weights when they were born August 31.

Zookeepers initially hand fed the cubs -- the first giant pandas born in Germany -- with bottles of milk pumped from mother Meng Meng but they now feed on their own.

She and father Jiao Qing came to Germany from China two years ago.

There are fewer than 2,000 of the endangered pandas estimated alive in the wild today.

The cubs have not yet been named or shown to the public.