Pakistan on Monday condemned an Israeli commando attack on a flotilla of aid ships bound for the Gaza Strip, describing the killings of up to 19 activists as "brutal and inhuman."
Prime Minister Yousuf Raza Gilani "strongly condemned" the attack on the "peaceful flotilla," his office said.
A group of Pakistanis had been travelling with the flotilla, and Foreign Minister Shah Mehmood Qureshi said the government was urgently seeking information about their well-being.
"It is a sad incident. The people and government of Pakistan strongly condemn it. There is no moral and legal justification for it," he told Pakistan's main private television channel Geo.
"The killing of members of this humanitarian mission, which also included women, is brutal, inhuman and constitutes a flagrant violation of international law and norms," Pakistan's foreign ministry said.
The government was "seriously concerned over the well-being and whereabouts" of Pakistani citizens and media personnel on board, it added.
There are no diplomatic relations between Israel and Pakistan.
In Islamabad, politicians, lawmakers and journalists staged a peaceful protest against Israel, denouncing the killings and calling on the United Nations and the United States to intervene.
Journalists also protested in the northwestern city of Peshawar, which has been hard hit by bombs blamed on Taliban and Al-Qaeda-linked militants.
Three Pakistanis, including an anchorman for a private TV channel, a producer and an aid worker were part of the flotilla, local media reported.
Israeli naval forces stormed the aid flotilla in international waters before dawn, killing up to 19 pro-Palestinian activists.
The bloody end to a high-profile mission to deliver supplies to the besieged Gaza Strip plunged Israel into a diplomatic crisis on the eve of talks between President Barack Obama and Israeli Prime Minister Benjamin Netanyahu.
Israel blamed passengers for initiating the violence, but activists from the ships accused Israeli commandos of starting to shoot as soon as they boarded.