SYDNEY (AFP) - Australian police on Monday urged the mother of a baby found dead and buried in the sand at a popular Sydney beach to come forward, as the city reeled from its second abandoned infant in days.

Two young boys playing at Maroubra beach found the decomposed body on Sunday morning, a week after another baby was found barely alive in a drain in western Sydney.

New South Wales state police commissioner Andrew Scipione urged the mother of the dead child to come forward. "Come and talk to us, seek some advice, we need to talk with you," he said, while also pleading with anyone who thought they might know something to speak to the authorities. "So if the particular woman won't come forward herself, please if you are a friend, a true friend, you will tell us because we think she might need some help."

The naked baby's body was found buried about 30cm in the sand, and the police said on Sunday it was not known whether it had been stillborn, had died after birth, or was killed. Its sex was not immediately obvious due to decomposition but a post-mortem revealed on Monday that it was a girl, the police said. There were no further details on how the child died or how long she had been in the sand.

The gruesome discovery by two brothers, aged six and seven, came exactly one week after another baby was found wrapped in a hospital-issued blanket down a drain, where it was believed to have survived for five days.

Passers-by were able to rescue the newborn after hearing its cries, and a 30-year-old woman was later charged with attempted murder.

New South Wales Police Minister Stuart Ayres said the cases raised the question of what could be done to help desperate families.

"There is no doubt we find ourselves with two cases that are currently under investigation that requires us to think seriously about what we need to help families that are in crisis," he said.