The intricate design of the improvised explosive device, sophisticated technology and the explosives used in Friday's blast at the historic Mecca Masjid in Hydrabad point towards involvement of terrorist groups, say police.
A deadly mixture of RDX and TNT is believed to have been used in the blast, which was triggered with the help of a cellular phone. Police suspect it to be the handiwork of Harkat-Ul Jihad al Islami (HUJI), the Bangladesh based terror group. However, they have not ruled out involvement of Pakistan-based terror groups Jaish-e-Mohammed (JeM) or Lashkar-e-Toiba (LeT), which trigger such blasts in Kashmir.
However, police are not able to give any hard evidence pointing to the involvement of these groups.
HUJI is the main suspect because of its local links and its suspected involvement in suicide bomb blast at Hyderabad Police Commissioner's (Task Force) office in Hyderabad in October 2005 that killed one policeman and injured another. Dalian, a HUJI activist, believed to be a Bangladeshi, had carried out the suicide attack.
Police now suspect that Mohammed Abdul Shahed alias Bilal, the mastermind behind the 2005 suicide attack, was also the brain behind Friday's blast at 17th century Mecca Masjid, a stone's throw from Charminar, the symbol of Hyderabad.
Bilal, a native of Hyderabad, is now believed to be based in Bangladesh. Police sources said the most wanted terrorist also had links with Pakistan based terror groups and had visited the neighbouring country and Saudi Arabia.
Director General of Police MA Basit said the kind of sophisticated mechanism used in the blast was not available in Hyderabad. Police sources believe that bombs could have been made across the border or someone trained by terror groups like HUJI, LeT or JeM.
Police are confident that they would get clues in a day or two about the perpetrators. They are pinning their hopes on a SIM card recovered from a mobile phone attached to an unexploded IED. The investigators are trying to trace the calls made or received from this SIM card.
It was sheer providence that bomb disposal squad defused the IED by separating the phone and explosive charge before the culprits made second call triggering its detonation.
The investigators are also trying to find out why two IEDs could not be triggered. While one IED was defused about 100 meters away from the scene of first blast, the second was defused three hours after the explosion. The bomb was found hanging from railing near the main gate.
"Had this bomb exploded several precious lives would have been lost," said a police official. Thousands of people including police officials and four ministers had crossed the gate to visit the scene of the first blast.
The use of mobile phone technology to trigger blasts involves sophistication. The detonator is connected to the mobile phone. After planting the bomb, the bomber calls up the mobile phone to trigger the blast. The call can be made from miles away from the blast site or even from abroad.
The bomb used in Friday's blast comprised a high explosive substance filled in a 10-inch by 3-inch pipe. A sophisticated material was used in the blast and this is believed to be a mixture of RDX and TNT taken from hand grenades and stuffed into metallic pipes. Each bomb weighed eight kg including the iron pipe and the explosives.