Two masked men on a bike flung acid on a 17-year-old who was attacked minutes after she left her west Delhi home for school on Wednesday morning and is battling serious injuries at Safdarjung Hospital's burn ICU, police said.

As outrage spread over the acid attack, women's groups and others, including Lt Governor V K Saxena, raised questions on the availability of acid in markets despite a ban and Delhi Chief Minister Arvind Kejriwal asked how the accused could have gathered so much courage.

The teen, who was with her younger sister when the attack took place at Mohan Garden near Uttam Nagar, has named two persons who could be responsible for the attack. Of them, one has been detained by police, said Deputy Commissioner of Police (Dwarka) M Harsha Vardhan.

"She has suffered seven to eight per cent facial burns and her eyes have also been affected. She has been admitted to the burn ICU and is stable," said a doctor at Safdarjung Hospital.

Waiting outside the burns ward, her father told reporters that her sister was with her at the time.

"My daughter left home at 7.30 am. As soon as she crossed the street, she was attacked. The incident happened within six to seven minutes of her leaving the house. My youngest daughter had gone along with her and then came running to us," he told reporters here.

Asked whether she was being harassed or stalked, he said she had made no such complaint.

Police is investigating whether the two men knew her.

Recapping the events of the morning, her uncle said she was walking towards the metro station with her sister when she was attacked. The pain must have been excruciating and she ran towards nearby shops for help. One shopkeeper poured milk on her face to alleviate the agony, he said.

"They were waiting for one of their friends so that they could take the metro from Dwarka Mor and go to school. Suddenly, two men on motorcycle arrived there and threw acid on her," the uncle told reporters.

The lt governor spoke to Delhi Police Commissioner Sanjay Arora on the matter.

"... (he) sought a detailed report into the incident, including as to how the acid used was procured despite a ban in the City.

"LG has instructed for swift and thorough investigation so as to ensure exemplary punishment to the guilty. The LG is in touch with the Hospital Authorities and has urged them to ensure the best treatment. He has also assured all possible assistance to the victim and her family," the handle Raj Niwas Delhi, run by the LG Secretariat, said on Twitter.

Kejriwal said these kind of attacks cannot be "tolerated at all".

"The accused should be given the strictest punishment. The safety of every girl child in Delhi is important to us," he said.

Police said the matter was reported to them around 9 am.

"A PCR call was received around 9 am regarding an incident of throwing acid on a girl in the area of Mohan Garden Police Station.

"It was stated that a girl aged 17 years was allegedly attacked with some acid-like substance by two persons on a bike around 7.30 am this morning," said DCP Vardhan.

The schoolgirl was initially admitted to Deen Dayal Upadhyaya Hospital and later referred to Safdarjung Hospital.

CCTV footage captured the horror of the morning. Police said it showed two people throwing acid at the girl on the sidewalk.

The National Commission For Women (NCW) has taken cognizance of the attack, while the Delhi Commission for Women (DCW) has issued notice to the police.

"Acid was thrown at a school girl near Dwarka Mor... Will get justice for the daughter. The Delhi Commission for Women has been fighting for years to ban acid in the country. When will the government wake up?" DCW chairperson Swati Maliwal wrote in a tweet in Hindi.

A district magistrate, requesting anonymity, said district authorities regulate the sale of acid.

"... we have a list of all the authorised sellers of acid who provide us regular sale reports. Also monitoring is ensured by the SDMs at sub-divisional level," he said.

Aam Aadmi Party National Spokesperson Saurabh Bharadwaj also raised concerns over the increasing crime rate in the national capital.

"LG Saab, you have Delhi Police and crime is increasing every day. Instead of interfering in the work of the Delhi government, you should concentrate on your work. After your arrival, crimes are increasing in Delhi," he tweeted in Hindi.

Following the increase in the number of acid attacks, the Supreme Court in 2013 banned over-the-counter sale of acid at retail outlets and ordered a compensation of Rs 3 lakh to be paid by state governments to each acid attack victim.