The ambush took place as the Sri Lankans were on their way to play a Test match against their Pakistani hosts at the Gaddafi stadium.
The BBC's Barbara Plett, in Islamabad, says accounts suggest the attack was sophisticated, with one group of gunmen firing a rocket-propelled grenade to create a diversion, while others fired on the convoy.
Sri Lanka's assistant coach Paul Farbrace, who is British, told the BBC: "There was a lot of shouting and people hitting the floor and when I got to the floor I realised that the blood that I could see was coming from me - luckily superficial wounds."
Sri Lankan wicket-keeper Kumar Sangakkara told Australia's ABC radio that he and his team mates probably owed their lives to their bus driver.
"We had an amazing driver who just kept driving the bus straight through all of that to the ground and that's probably what saved us."
The driver of a bus following behind, carrying the Australian umpires, was killed.
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
Two members of the Sri Lankan team, Thilan Samaraweera and Tharanga Paranavitana, were sent to hospital but later released.
Grenades, rocket launchers and backpacks belonging to the attackers were found at the scene, police said.
Following the attack, New Zealand said a cricket tour of Pakistan due later in the year was now unlikely, and the International Cricket Council (ICC) cast doubt on the country's ability to host high-level games.
"It's difficult to see international cricket being played in Pakistan for the foreseeable future," ICC chief executive Haroon Lorgat said in London.
ICC President David Morgan said the attack had changed the whole landscape for international cricket.
Pakistani cricket was already suffering from serious security concerns.
Last month the ICC decided not to hold the 2009 Champions Trophy there due to safety worries.
It is now considering whether Pakistan can co-host the cricket World Cup, due to be held across four South Asian countries in 2011.
Pakistan invited Sri Lanka to tour only after India's cricket team pulled out of a scheduled tour following the Mumbai attacks.
The Pakistani politician Imran Khan, a former captain of the country's cricket team, said the Sri Lankan visitors had been given inadequate protection.
"This was one of the worst security failures in Pakistan," he said. "The Pakistan government guaranteed the Sri Lankan cricket team that they would provide them security."
Our correspondent says security forces will be investigating any connections to al-Qaeda and Taleban militants as well as Kashmiri jihadi groups.
Sri Lankan President Mahinda Rajapakse condemned the "cowardly terrorist attack" and ordered the players' evacuation back to Sri Lanka. They flew back to Colombo later in the day.
Pakistani President Asif Ali Zardari also condemned the attack, and ordered an immediate investigation "so that the perpetrators are identified and their motives exposed", said a statement from his office.
A spokesperson for India's foreign ministry urged Pakistan to take "prompt, meaningful and decisive steps to dismantle the terrorist infrastructure once and for all".
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