Indonesian police are investigating an advertisement offering two babies for sale at $US1000 each after it was spotted on a popular auction and shopping website.
"We are still investigating the existence of the online advertisement," Jakarta police spokesman Rikwanto told reporters on Monday.
"We have asked Tokobagus how the advertisement came to be posted, for how long, and whether any transaction was made," he added.
The National Commission for Child Protection lodged a police report last week after spotting the posting, its chairman Arist Merdeka Sirait told AFP.
"There was a photo of a baby and a telephone number. We called the advertiser and he said he wanted to sell two 18-month-olds, a boy and a girl, for Rp 10 million each," Sirait said.
"We were negotiating, talking about birth certificates when he suddenly hanged up. We tried contacting him again but failed," he added.
"This seems to be a new modus operandi by baby-selling syndicates. We are very concerned and must stop this crime against humanity," Sirait said, adding that human-traffickers could be jailed from 15 to 20 years.
Tokobagus posted an apology on Twitter, saying the advertisement was a result of "pure human error and was unintentional" and had been removed.
Indonesians have been using local auction and shopping sites to sell anything from cars and jewellery to body organs such as kidneys, exploiting a loophole in local laws.
Hundreds of advertisements have appeared on Indonesian personal advertising websites offering kidneys for as little as 50 million rupiah each.