Banned Harkat-ul-Jehadi Islamia, operating from Bangladesh, is believed to be behind the serial blasts that rocked the tourist city of Jaipur on Tuesday evening, killing nearly 50 people besides injuring several others.

Though baffled by the attack as Jaipur was not on the terror radar, sources said the tell-tale signs of the blasts indicate HuJI's hand.

The blasts showed that HuJI, which is being mainly run from Bangladesh, has managed to establish cells in Rajasthan and that the outfit was responsible for previous major terror attacks, including the New Year eve attack on CRPF camp in Rampur and serial blasts in three other places in Uttar Pradesh.

The last terror strike in Rajasthan occurred on October 11, 2007 when an explosion in the Dargah of Khwaja Moinuddin Chishti in Ajmer left two persons dead and 17 others injured.

HuJI outfit, suspected to be behind the blast at the sufi shrine, had used a mixture of Tri-Nitro Toluene as the explosive material.

In Tuesday's blasts also, pieces of iron pipe were used by militants as splinters that pierced through victims at the crowded places in the Pink city.

The sources did not rule out the possibility that banned HuJI may have been supported by Jaish-e-Mohammed (JeM), which has been attempting to target tourist destinations and places of economic interests.

The intelligence agencies have already started analysing STD and international calls made out of Jaipur during the last 48 hours.