Since 1980, China has limited most couples to one or two children, depending on location, occupation and ethnicity, as it has sought to limit the growth of its ballooning population, now at 1.3 billion.
The offspring of China's ''one-child policy'', which covers most city-dwellers, are free to raise two children under an exemption for couples who are both only children.
''If the ageing of the population continues, this will have a certain effect on social and economic development, and on employment and social security,'' Xinhua said, citing a report from Guangzhou's official family-planning agency.
By 2010, Guangzhou would be home to more than 1 million people over 60 years of age, but would only be able to accommodate 40,000 in aged care homes, the China Daily said in a separate report.
The capital of the southern province of Guangdong had a reported population of about 7.7 million at the end of 2005.
By 2035, people over 60 would number some 2.3 million at current growth rates of 4 per cent a year, the newspaper said, citing the family-planning agency.
China has defied calls from some Western governments and organisations to scrap its family planning laws, saying they have prevented 400 million births and boosted prosperity in a country that already has one-fifth of the world's population but only seven per cent of its land.
The family-planning policy has exacerbated a gender imbalance in China, where easy access to ultrasound tests and gender-selective abortions have resulted in 118 boys born for every 100 girls.
That imbalance has led to other social problems, including cases of women being kidnapped and sold to men who could not find marriage partners.
In recent months, the country has cracked down on the growing ranks of affluent couples willing to pay steep fines as punishment for having extra children.
Officials in China's eastern Anhui province slapped a record 600,000 yuan (dollar 78,980) fine on a private entrepreneur for flouting family planning laws, state media reported in May.