Players from industries such as water, waste management and urban planning are gathering in Singapore starting from Sunday for three concurrently held sustainable cities events.

The Singapore International Water Week, the World Cities Summit and the inaugural CleanEnviroSummit Singapore opened on Sunday, with some 15,000 leaders, experts and delegates from around the world.

More than 900 companies from a wide range of sectors like water, energy, environment, waste, information technology, architecture, planning, financing and real estate were participating in the events, organizers said.

Singapore Prime Minister Lee Hsien Loong said sustainable development will be the key to addressing the challenges arising from the urbanization of the world on "an unprecedented scale."

More than 2.5 billion people will move to cities worldwide by 2050, driven by emerging economies, particularly Asia, he said.

In China, about 320 million people are expected to move to the cities by 2050, bringing the total urban population in the country to 1 billion. In India, 488 million people will move to the cities over the same period.

Cities can be better places to live, but it calls for proper planning, efficient administration and public support to make cities work, Lee said.

The three co-located events will run for five days.

Lee said Singapore has always been committed to sustainable development and has made efforts to develop itself as a liveable and sustainable city, citing the concept of garden city, managed consumption of scarce resources such as water and energy.

Singapore will try to build a "City in a Garden" over the next phase to bring green spaces and biodiversity to the doorsteps, he said.

The city state managed to develop a vibrant water sector while making efforts to address its strategic vulnerability of water shortage over the past decades. The government encourages research and development in the water sector by putting in place incentives such as the Lee Kuan Yew Water Prize.

It was ranked the top Asian city in Mercer's 2011 Quality of Living worldwide survey, and top in environmental sustainability in Siemens' Asian Green City Index 2011, respectively.

The International Water Week and other sustainable cities events will allow industry players from around the world to share their experiences and best practices in water, urban development and green practices.