According to Dawn News, Uzbek militants fighting with the Pakistani Taliban say they carried out Sunday's deadly assault on Karachi's international airport.
The Islamic Movement of Uzbekistan posted photos of 10 men in black turbans holding assault rifles who had sought revenge for military air strikes.
At least 39 people were killed in the airport raid, including all 10 gunmen.
DNA tests are being conducted on the gunmen, who officials in Karachi said appeared to be of Uzbek origin.
The BBC's Shahzeb Jillani in Islamabad says the Islamic Movement of Uzbekistan (IMU) is a highly trained militant group, with bases in the North Waziristan tribal region.
It works closely with al-Qaeda and Taliban militants and has previously carried out large-scale co-ordinated attacks in Pakistan, including one on Peshawar airport in 2012. In its statement the group said the Karachi raid was to avenge military air strikes in Pakistani tribal areas last month which it alleged had killed women and children.
Sunday's assault was followed by a second gun attack near the airport on Tuesday, raising tensions in Karachi further. Gunmen shot at a security camp outside the airport perimeter but there were no casualties.
The violence follows a major split in the Pakistani Taliban (TTP) and faltering peace talks between the militants and the government.
Pakistan's leaders met to discuss security on Tuesday. The military have been targeting militants in the tribal north-west but it is still not clear whether a broader military offensive in the Taliban stronghold of North Waziristan could be given the political go-ahead.
Local media said the meeting had authorized the army to carry out "appropriate action" against terrorist groups.
Prime Minister Nawaz Sharif had pledged peace talks with the TTP during his election campaign.
Talks began in March, but little progress was made and violence has continued.
Security forces gained control following an overnight battle, and the airport reopened late on Monday.
On Wednesday another body was recovered from the airport, bring the total number killed to 39, including the attackers. Officials said the dead man was an airport security force official.
The Taliban have declared in statements that the wave of attacks will continue.
Correspondents say residents in Karachi have been shocked by the brazenness of Sunday's airport attack.
Pakistan has been fighting an Islamist insurgency for more than a decade, with the Pakistani Taliban the main militant grouping. Early on Tuesday the Pakistani military carried out air strikes in tribal areas in the north-west Khyber region, killing at least 15 militants, officials say.
The terrorist attacks should raise many questions:
1. Why is Pakistan the only target: Mainly because of its alliance with the United States and the West in the international war on terrorism. What about other countries who are partners in fighting terrorism across the globe. Are those countries facing such extreme terrorism as Pakistan does?
2. Why are foreign terrorist organizations involved: I have pointed out earlier that another aim of terrorism is to destabilize and defame Pakistan as a country on the whole. There are countries and non-state actors who are involved in training, financing and arming the insurgents on their own soil and then sending them across the border into Pakistan. Afghanistan has played a major role in becoming a conduit of arms, drugs, money and terrorists to Pakistan.
3. Why was the biggest airport targeted: Karachi is the economic hub of Pakistan; targeting its main air terminal means striking its civil aviation industry, creating a sense of insecurity for other airlines and causing economic damage.
4. Who plans the attacks: Planning terrorist attacks with such grandiose design is not the work of teenage students attending religious schools. At the most they are capable of killing a few innocent people on the city streets. Such well- structured terrorist activity combines common interest, secret dealing, illegal financing, acquisition of modern weapons, recruiting, training, intelligence gathering and above all state sponsorship. The foreign based pay masters are hidden from the common eye but not impossible to unearth.
Pakistan has taken the decision to carry out the military operation against the terrorist strongholds in North Waziristan, till the terrorists are eliminated. The United States has supported this decision. For a long-term solution to the problem of terrorism, Afghanistan will have to take difficult decisions. It will have to check illegal opium production and smuggling, eliminate terrorist training camps on its soil, establish strict border controls through security check points and try to maintain a democratic political system. With the withdrawal of foreign forces in 2014, it is left with no choice but to offer a hand of trust and friendship to Pakistan. Peace will never be established without mutual cooperation.
Dawn News June, 16 2014
BBC News June 14, 15, 16 2014