By M Ilyas Khan
BBC News, Islamabad
There has been much speculation over the gunmen's identity
Who could have done it?
The video footage of the assault on the Sri Lankan cricket team in Lahore is a stark reminder of the November attacks in the Indian city of Mumbai, in which about 10 suspected militants held the city hostage for three days.
A similar number of men staged an equally audacious attack in Lahore. They ambushed the bus that was taking the Sri Lankan team to the stadium for a match with Pakistan.
Though the targets of the two attacks were vastly different, the attacks themselves were both spectacularly staged against high-value targets and made international headlines.
The style of these attacks is also reminiscent of an attack by a group of militants on the Indian parliament in the winter of 2001.
The Indian authorities blamed that attack - and the Mumbai assault - on a Pakistan-based militant group, Lashkar-e-Taiba (LeT).
After some procrastination, the Pakistani authorities also endorsed the Indian claim in relation to the Mumbai attacks, saying at least nine men affiliated with LeT had sailed out from its southern port city, Karachi, to attack the Indian financial hub.
The shooting began near the Gaddafi stadium
It has arrested several top LeT leaders in connection with that attack.
Could it be, then, that the LeT has turned back on Pakistan to even scores?
LeT is one of a number of militant groups that are believed to have been raised, trained and funded by the Pakistani security apparatus to fight Indian troops in the disputed region of Kashmir.
It is generally considered to be sympathetic to Pakistani security interests in the region - and analysts doubt that it would try to destabilise a Pakistani government unless it had been given a nod from within the security establishment.
That establishment has been blamed in the past for using militants, especially sectarian outfits, to destabilise civilian governments during the 1990s.
The attack in Lahore has happened at a time when a civilian government is in power after eight years of military rule.
The government has made some diplomatic concessions to India which the military - which considers India as the enemy - may not like.
In addition, the air of reconciliation that was born at election time a year ago is giving way to political discord, with anti-government agitation brewing in the Punjab province, where the attack took place.
Cricketers Thilan Samaraweera (L) and Tharanga Paranavitana were injured
So, have the suspected "rogue" elements in the security establishment decided to rock the boat for a government that appears increasingly vulnerable to the threat posed by militants?
Some in international quarters have suggested that Sri Lanka's Tamil Tigers separatist group could possibly be involved in the attack.
The Tigers have been conducting an insurgency in the northern parts of Sri Lanka since the mid-1980s and are currently losing ground to the Sri Lankan army.
In recent weeks, the Tigers have seen key towns fall to the military, prompting many to speculate that it is the beginning of the end of their insurgency.
But could the Sri Lankan rebel group make a desperate move like this one to stage a comeback?
Analysts say they are not known to have operated in Pakistan in the past, and do not have the kind of logistics and network in the region that they would require to stage an attack of this nature.
Besides, they are unlikely to blow up the entire Sri Lanka team - as the attackers tried to do by lobbing grenades under their bus - because it also includes ethnic Tamils.
Another potential suspect are the Pakistani Taleban, or Islamist militants who are conducting a bloody insurgency in the north-west of the country.
They have been blamed, or claimed responsibility, for a number of equally spectacular attacks in Pakistan in the past.
One of the groups was even accused by the government of having carried out the December 2007 assassination of former Pakistani Prime Minister Benazir Bhutto.
But they largely depend on suicide attacks or remote-controlled improvised explosive devices (IEDs) and their targets have been either state officials or members of rival sects.
Al-Qaeda, which many believe to be an umbrella organisation of most militant groups active in Afghanistan, Pakistan and Kashmir, appears to have had a role in planning previous attacks against high-profile targets in Pakistan, such as foreign dignitaries.
Many security analysts suspect its role in a number of bombings against restaurants and foreign missions in the Pakistani capital, Islamabad.
Analysts say al-Qaeda considers an Islamic Pakistan as essential to its pan-Islamist ambitions. It has been at odds with successive Pakistani governments because of their "pro-West" policies.
Meanwhile, many Pakistani ex-military security analysts claim that Tuesday's attack might be the handiwork of the Indian intelligence service, Research and Analysis Wing (Raw).
Some of them, such as former intelligence chief Lt Gen Hamid Gul, also blame Raw for the Mumbai attacks. There is no evidence to support such a claim.
Gen Gul and others point out that both these attacks have put Pakistan in a bad light and eroded its ability to withstand international pressure in matters pertaining to its national interests.
This, they believe, is part of a plot by India to undermine Pakistan.
Pakistan has ordered a high-level investigation into the Lahore attack, with President Asif Zardari pledging that the perpetrators should be revealed.
If this happens, it would be unprecedented.
Militant attacks in all parts of the world have been investigated and solved, but Pakistan is yet to solve even one out of the hundreds of attacks it has suffered since the 1980s.