A senior NIA official, who requesting anonymity, said the arrested accused were taken to several parts of a western Uttar Pradesh city to identify the people who supplied material for making the pipe bombs.

The official also said the agency carried out fresh searches at two places in Amroha to identify more suspects and took two persons for questioning.

He said the agency rounded up two scrap dealers, Ram Chander and Pintu, from the bypass area of Amroha.

According to the official, the two people were in touch with the brother duo, Raees and Saeed, who worked as welders and were arrested on December 26.

The counter-terror probe agency also questioned two general store shopkeepers from Amroha, from whom the alleged mastermind Mufti Mohammad Suhail bought pottasium to make bombs. However, they were released after questioning.

On December 26, the NIA arrested 10 people, including the group leader, who were allegedly planning to attack some political personalities, security establishments as well as crowded places in Delhi and the National Capital Region.

The arrests were made after the NIA carried out searches at 17 places -- six in East Delhi's Jafarabad area, six in Amroha, two each in Lucknow and Hapur and one place in Meerut, leading it to seize a country-made rocket launcher, 12 pistols, 112 alarm clocks, 100 mobile phones, 135 SIM cards, several laptops and various electronic gadgets, besides 150 rounds of ammunition.

The NIA also seized 25 kg of explosive material, such as potassium nitrate, ammonium nitrate, sulphur, sugar material paste, mobile phone circuits, batteries, 51 pipes, remote control car triggering switch, wireless digital doorbell for remote switch, steel containers, electric wires, knife, sword, IS-related literature and Rs 7.5 lakh in cash.

All the arrested members of 'Harkat-ul-Harb-e-Islam' are in NIA custody.

The agency had registered a case on December 20 under several sections of the Indian Penal Code (IPC), the Explosive Substances Act and the Unlawful Activities (Prevention) Act.