They were arrested from west Delhi's Pankha Road Sep 24 while receiving a consignment of heroin.
Theophilus, 29, resident of Agbor in Nigeria and Gurpreet, 24, hailing from Punjab, have been residing here in the capital since 2009.
They smuggled drugs through the India-Pakistan border and supplied them in Delhi and Mumbai for sale. Around 3.995 kg heroin was recovered from Gurpreet and 4.015 kg was recovered from Theophilus.
"Theophilus revealed that he had come to India in 2008 on a business visa and settled in Delhi after expiry of his visa. In 2009, he came in contact with an international drug mafia having links in Afghanistan, Pakistan, Punjab, Delhi and Mumbai," said Sanjeev Kumar, deputy commissioner of police.
"According to him, he operated on the instructions of his Nigerian counterpart based in Pakistan. They sent the consignment of heroin from Pakistan to India through the India-Pakistan border in Punjab," said the officer.
Theophilus used to send his associate to Punjab to collect the consignment. Till date, he has received around six consignments of heroin of various quantities.
Gurpreet Singh, who came to Delhi in 2009 and worked in a private firm became an associate of Theophilus a few months back.
Efforts are being made to identify the drug traffickers in Punjab, Delhi and Mumbai involved in the drug ring.