The heroin was smuggled into India from Afghanistan through Pakistan and Jammu and Kashmir.
A Nigerian national was arrested for allegedly supplying heroin to drug dealers and four kg of the narcotic, worth Rs 20 crore, was seized from him, police said on Monday.
Oliver Chijike Iheanacho was arrested from the Majnu Ka Tila area on the Ring Road in north Delhi, they said.
Four kilogram of heroin, worth Rs 20 crore in the international market, was seized from him, police added.
He was caught on the intervening night of May 1 and 2, they said.
During interrogation, he revealed that he used to receive heroin from his associates based in Afghanistan, said PS Kushwah, Deputy Commissioner of Police (Special Cell).
The seized heroin was to be delivered to a Punjab-based drug dealer, they said.
The heroin was smuggled into India from Afghanistan through Pakistan and Jammu and Kashmir.
These couriers used to hand over the heroin to him in Delhi and he used to further supply it to drug dealers in Delhi and Punjab, said the DCP.
He also used to get his consignment of drugs from his associates in Delhi who are of African-origin, he said.
The accused also revealed that he used to send consignments of heroin to other countries including England, France, Canada and South Africa through courier companies, the officer added.
Efforts are being made to identify and arrest other persons involved in the racket from Delhi and Punjab.
Some travel documents suspected to be forged have also been seized from the accused. These are being verified, police said.
Iheanacho came to India in 2013 and after spending some time in Mumbai, he shifted to Delhi. In Delhi, he came in contact with people of African-origin involved in supplying drugs in west Delhi.
Even after the expiry of his visa, he did not return to his country and continued to stay illegally in India and indulged in drug peddling, he said.