The World Autism Awareness Day is being observed on 2 April.
The day was unanimously declared as World Autism Awareness Day by the United Nations General Assembly in 2008 to highlight the need to improve the lives of children and adults who suffer from autism.
Autism is a lifelong developmental disability that manifests itself during the first three years of life and results from a neurological disorder that affects the functioning of the brain.
The disorder mostly affects children and is prevalent across countries, genders, races and socio-economic backgrounds.
"The rate of autism in all regions of the world is high and it has a tremendous impact on children, their families, communities and societies," the UN said in a statement.
Children affected by autism have impairments in social interaction, problems with verbal and non-verbal communication and show restricted or repetitive behaviour, interests and activities.
Scientists presume distinct causes for the complex disorder.
A recent study by the University of Chicago suggests that exposure to air pollutants can dramatically increase a child's chances of developing autism.
According to a more recent research study by the University of California, the San Diego School of Medicine and the Allen Institute for Brain Science, autism begins during pregnancy and is largely genetic.
2014: Call for action
This year's World Autism Awareness Day marks the celebration of the creative minds of people with autism and calls for all possible opportunities for education, employment and integration for them, according to the UN.
"World Autism Awareness Day is about more than generating understanding; it is a call to action. I urge all concerned to take part in fostering progress by supporting education programmes, employment opportunities and other measures that help realise our shared vision of a more inclusive world," UN secretary general Ban Ki-moon said.
The United Nations has organised a number of events to mark the day and create awareness about autism.
A screening of the movie El Pozo (The Well) was held at the UN headquarters in New York on 1 April. The Argentina film tells the story of Pilar, a 26-year-old autistic woman, who does not communicate with other people and lives in her own world of fantasies, until her family takes a decision that will change the course of their lives.
Besides the UN, Autism Speaks, an autism advocacy organisation in the United States, is celebrating the day with fundraising and awareness-raising events.
The organisation's Light It Up Blue campaign to spread autism awareness sees famous buildings around the world lit blue on World Autism Awareness Day every year.