Asia has welcomed the world's first symbolic 7 billionth baby, but celebrations were tempered by worries over the strain that humanity's population explosion is putting on a fragile planet.

The United Nations said by its best estimates the 7 billionth baby would be born on October 31, and countries around the world have planned events surrounding the demographic milestone.

Zambia is throwing a 7 billion song contest; Vietnam is staging a 7B: Counting On Each Other concert; Russian authorities are showering gifts on selected newborns and Ivory Coast is putting on a comedy show.

The Philippines was the first country to declare a 7 billionth baby, in the form of a girl called Danica May Camacho.

Weighing 2.5kg, Danica was delivered under an explosion of media camera flashes at Manila's Jose Fabella Memorial Hospital.

"She looks so lovely," mother Camille Dalura whispered as she cradled her baby.

"I can't believe she is the world's 7 billionth."

Danica is the second child for Dalura and her partner, Florante Camacho, who stood quietly in a corner wearing a white hospital gown as television crews and photographers crowded to get a shot of his daughter.

UN officials presented the child with a cake. Other gifts came from local benefactors including a scholarship grant and a financial package to help the parents open a general store.

Also on hand to witness the birth was 12-year-old Lorrize Mae Guevarra, who the Philippines declared as its own 6 billionth baby when the world reached that landmark in 1999.

"I am very happy to see this cute baby. I hope like me she will grow up to become healthy and well loved by everyone," Lorrize said.

The UN named a Bosnian child, Adnan Mevic, as the Earth's 6 billionth inhabitant on October 12, 1999. The secretary general at the time, Kofi Annan, was pictured in a Sarajevo hospital with Adnan in his arms.

The Mevic family is now living in poverty, which is partly why no single baby will be put in the global spotlight this time.

Instead, Danica May Camacho is one of a number of children whose birth will be marked throughout the day.

The world has added a billion babies - or almost another China - since Adnan Mevic was born. Having taken millennia to pass the 1-billion mark, the world's population has doubled in 50 years.

See how the world's population has grown through the centuries. Source: http://www.worldometers.info/world-population; UN population division and US Census Bureau

'World of contradiction'

Mounting concern over humanity's environmental impact and fears we may not be able to feed ourselves in 100 years' time have cast a cautionary tone over the build-up to the 7 billion milestone.

UN chief Ban Ki-moon will not be seen cuddling a newborn. He has said the 7 billionth baby will be entering a "world of contradiction", especially if the child is born on the wrong side of the poverty line.

"Plenty of food, but still a billion people going to bed hungry every night. Many people enjoy luxurious lifestyles, but still many people are impoverished," he said in an interview with Time magazine.

Addressing students at a New York school last week, he said: "This is not a story about numbers. This is a story about people."

"Seven billion people who need enough food. Enough energy. Good opportunities in life for jobs and education. Rights and freedoms. The freedom to speak. The freedom to raise their own children in peace and security.

"Everything you want for yourself - 7 billion times over."

With about two babies being born every second, the 7 billion figure will keep racing ahead in decades to come - to more than 10 billion by 2100, according to UN estimates.

The UN predicts India will overtake China as the world's most populous nation by 2025, when it will have almost 1.5 billion people.

AFP