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

The United Nations says that by its best estimates the seven billionth baby will be born somewhere on October 31, and countries around the world have planned events surrounding the demographic milestone.

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

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

Weighing 2.5 kilos (5.5 pounds), Danica was delivered just before midnight Sunday under an explosion of media camera flashes at Manila's Jose Fabella Memorial Hospital.

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

"I can't believe she is the world's seven 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 six billionth baby when the world reached that demographic 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," Guevarra said.

The UN named a Bosnian child, Adnan Mevic, as the Earth's six billionth inhabitant on October 12, 1999. The secretary general at the time, Kofi Annan, was pictured in a Sarajevo hospital with Mevic 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 one-billion mark, the world's population has now doubled in 50 years.

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 buildup to the seven billion milestone.

Current UN chief Ban Ki-moon will not be seen cuddling a newborn. He has said the seven 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 -- seven billion times over," he said.

The UN chief will be taking his message to the Group of 20 summit this week, where leaders of rich and developing nations will discuss the threat of global recession and efforts to tighten rules on bankers' bonuses and tax havens.

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

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

A new UN Population Fund (UNFPA) report highlights how the world will face growing problems finding jobs for the new army of young people, especially in poor countries.

It also sounds alarms over how climate change and population growth are adding to drought and famine crises; the management of megacities like Tokyo; and ageing populations such as Europe's.

"This is not a matter of space -- it's a matter of equity, opportunity and social justice," UNFPA executive director Babatunde Osotimehin said.

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