S.N. Srivastava, special commissioner of Delhi Police, said Tehsin Akhtar alias Monu, 22, had been taken into custody. But he declined to say when and where the man was caught.

IANS had reported Akhtar's arrest Monday evening. 

Police officials described the arrest as a major breakthrough in the war against the shadowy group which has been blamed for several terror attacks in the country.

Police sources had earlier told IANS that Akhtar, a resident of Samastipur in Bihar, was part of the Indian Mujahideen's plan to create mayhem during the staggered Lok Sabha polls starting April 7.

The sources said Akhtar was in touch with Waqas, who was arrested Friday from Rajasthan also by Delhi Police.

Akhtar was reportedly involved in several bomb attacks across the country since 2010.

These include a blast at Varanasi's Sheetla Ghat during the evening 'aarti', a cooker bomb blast outside Jama Masjid in Delhi the same year, the 2011 serial blasts in Mumbai, the 2012 blasts in Pune and the twin bombings in Hyderabad in 2013.

All these attacks left a total of 43 people dead and 253 injured.

Following an Intelligence Bureau alert, Delhi Police arrested Waqas, a Pakistani, and his associates Mohammad Mahruf, Mohammad Tasleem Raza and Shaquib Ansari from Jaipur and Jodhpur in Rajasthan Friday and Saturday.

Delhi Police announced these arrests Sunday.

Police recovered explosives, detonators and electronic circuits and timers from the arrested men.

Srivastava told IANS that Akhtar was the one who received Waqas at the Kathmandu airport in September 2010 and brought him to Delhi to carry out the Jama Masjid bomb attack.

Police sources believe that Akhtar was being controlled by the India Mujahideen's absconding leader Riyaz Bhatkal, who is involved in several terror attacks in India.