The as-yet-unnamed baby boy was born in the city's University Clinical Centre at 0002 local time (2202GMT) on Tuesday - which the UN chose as "D6B", the day when humanity would pass the symbolic threshold.

Despite UN officials earlier saying Mr Annan's presence in the Bosnian capital was purely coincidental and there was no particular reason a Sarajevo baby had been selected, the UN chief acknowledged the symbolism of the birth in a city still scarred by years of war.

Mr Annan says the baby should be a symbol for tolerance in Sarajevo

Speaking at the hospital, Mr Annan said the event should be a spur towards restoring "the tolerance and multi-religious atmosphere that once characterised Sarajevo and Bosnia".

"The birth today of the six billionth person on the planet - a beautiful boy in a city returning to life, to a people rebuilding their homes, in a region restoring a culture of coexistence after a decade of war - should light a path of tolerance and understanding for all people," he said.

Hospital officials say the 3.55kg (8lb) boy and mother, 29-year-old Fatima Nevic, are both doing well.

Symbolic date

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"It is very fortunate and a pleasure for the entire staff of the clinic ... for this event to happen here," said hospital paediatrics chief Dr Idris Bukvic.

Population experts concede that D6B is purely a symbolic date.

With more than 3 babies born around the world every second, it is impossible to work out which baby is the world's six billionth.

(Click here to see a graph of world population growth)

Most demographers said the baby was more likely to be born in Asia than Bosnia.

The BBC's Owen Bennett Jones reports from Pakistan where population will double by 2035

The symbolic birth coincided with China defending its controversial birth-control policy.

"Without taking effective measures to slow down the rapid growth of its population, China would have 300 million people more than the current figure of 1.248 billion," senior family planning official Zhang Weiqing was quoted as saying by the official Chinese news agency.

China operates a one-child policy which has earned it praise and vitriol in almost equal measure.

Population explosion

Sarajevo is still rebuilding after the bitter Bosnian war

UN population experts say the country has made sacrifices for the benefit of the whole world, but human rights groups argue the policy infringes civil liberties and encourages forced abortions.

China denies this, although it admits that occasionally local officials overstep the line.

In the end D6B and Baby Six Billion were chosen by the UN to highlight the problems of the world's population explosion.

BBC Beijing Correspondent Duncan Hewitt: "Loopholes in the law could mean more children for China"

At the Sarajevo hospital Mr Annan warned of the huge challenge that the world faced in coming years "to feed, to clothe and house" its growing population.

Although the growth rate has slowed in recent years, the world population has doubled since 1960 and the UN estimates that the vast majority of new-born infants will grow up to be poor and illiterate.

"The challenge to feed and clothe and house this great mass of humanity over the next decades will be immense," Mr Annan said.

"The means, however, are available. The question is whether we will have the will."

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