The Delhi Police Crime Branch, which made the arrests, said the accused used to send text messages and e-mails to the unsuspecting victims informing them that they had won huge amounts in lottery schemes.
"Then they used to seek details of the victims such as their names, addresses, phone numbers and e-mails. They used to send false documents to the victims and then ask them to deposit money for income tax, service charge, conversion charge etc.," said Deputy Commissioner of Police (Crime Branch) G Ram Gopal Naik.
On June 23, a trap was laid by the Crime Branch sleuths at a bus stand in south Delhi's Malviya Nagar and two of the accused were arrested. Four mobile phones, fake US dollars, three laptops and passports were seized from their possession, said Naik.
Two more arrests, including that of the Indian woman, were made subsequently.
The Nigerian High Commission has been informed of the arrests.