Mourners lay wreaths at the site of the attack in Lahore
Pakistan President Asif Ali Zardari has vowed that those who attacked the Sri Lankan cricket team will be caught, and punished "with iron hands".
He said progress was being made on finding the gunmen who shot dead six policemen and drivers and injured eight Tour members in Lahore on Tuesday.
The Sri Lankan team earlier arrived back in Colombo amid emotional scenes.
Meanwhile, ICC match referee Chris Broad accused Pakistani security forces of "vanishing" during the attack.
"I am extremely angry that we were promised high-level security and in our hour of need that security vanished," said Mr Broad, who was caught up in the attack.
His claims were strongly denied by Ijaz Butt, chairman of the Pakistan Cricket Board, who referred to the policemen killed by the attackers.
Pakistan's President Zardari assured visiting Sri Lankan Foreign Minister Rohitha Bogollagama in Islamabad that "progress has been made in the investigation and the perpetrators will be exposed and brought to justice".
Chris Broad says he is 'angry' about the lack of security
He admitted that the attack was "a serious setback that had also undermined the sport of cricket in Pakistan".
Mr Zardari welcomed Sri Lanka's assertion that the attack would not harm ties and called for the two nations to work together to "learn from each other's experiences in fighting terrorism".
Up to 14 gunmen were involved in the attack at the Liberty Square roundabout in the heart of Lahore on Tuesday.
The BBC's M Ilyas Khan in Islamabad says hundreds of people have been questioned in poorer areas of Lahore to find clues to the attackers.
A number of people have been detained for further investigation but senior police official Haji Habibur Rehman told the Associated Press news agency that little headway had been made in identifying the men.
Sept 08: 54 die in an attack on the Marriott hotel in Islamabad
June 08: Six killed in car bomb attack near Danish embassy in Islamabad
Dec 07: Former PM Benazir Bhutto assassinated along with 20 others at a Rawalpindi rally
March 06: Suicide car bombing kills US diplomat in Karachi
June 02: 12 killed in car bomb attack outside US consulate in Karachi
May 02: 11 French engineers and three Pakistanis killed in an attack on Karachi Sheraton hotel
The police have registered a criminal case against unidentified men, saying they fired rocket-propelled grenades, threw grenades at the bus and fired automatic weapons, killing seven people and injuring eight.
Investigators are checking a number of backpacks recovered from nine locations in the city that were apparently left by the attackers as they escaped.
Police say the backpacks contain water bottles and dry food items, indicating that the attackers were preparing for a long operation, as was the case in last year's attacks in the Indian city of Mumbai.
Mumbai was blamed on the Pakistan-based group Lashkar-e-Taiba.
They have been mentioned as possible perpetrators of Tuesday's attacks, along with al-Qaeda and Taleban militants.
The government of Punjab province has placed advertisements in local newspapers announcing a $125,000 (£89,000) reward for any information that leads to the attackers.
The advert, carried on most front pages, features two grainy pictures of the attackers, apparently taken from video footage.
Chris Broad, who was to referee the abandoned Third Test, angrily attacked the Pakistani security services for their conduct during the attack.
He said he had raised security concerns with the Pakistan Cricket Board (PCB) before the tour started, and been assured of "presidential-style security".
But he said video footage shot during the attack showed "terrorists shooting past our van, sometimes into our van - and not a sign of a policeman anywhere. They had gone, left the scene, and left us to be sitting ducks."
But PCB chairman Ijaz Butt denied the claims.
"How can he say that when six policemen died in the attack? I will talk to him tomorrow morning and then give my full reaction," the AFP news agency quoted him as saying.
UK Prime Minister Gordon Brown on Wednesday called the attack "tragic", adding: "I've been pressing for some time the Pakistan government to make sure that arrests happen, that terrorists are brought under control."
BBC defence and security correspondent Rob Watson says there is Western concern that Pakistan does not have the necessary counter-insurgency fighting capabilities to tackle militants even if the political will is there.
But he says Western officials also believe there is a growing realisation among many in Pakistan's security establishment that the extremist Islamist network they helped to create over the years is now a threat to the Pakistani state's existence.
Residents in Lahore have converged on Liberty Square to pay homage to the policemen killed in the attack. The residents held prayers and laid wreaths.
Meanwhile, the Sri Lankan team's return to Colombo saw emotional reunions with anxious family members at the international airport.
"There were just these images of life flashing through my mind; all the while bullets were being sprayed at our bus, people around me were shouting," spin bowler Muttiah Muralitharan told the AFP news agency.
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