More than 300 Pakistani nationals are feared to have been killed after an overcrowded boat with around 750 people on board sank off the coast of Greece, a senior leader has said, even as at least 12 persons suspected of human trafficking were arrested from different parts of Pakistan.

At least 400 Pakistanis, 200 Egyptians and 150 Syrians, including around two dozen Syrian women and young children were on the packed boat when it capsized in open seas off Greece last week.

Senate Chairman Muhammad Sadiq Sanjrani disclosed the numbers on Sunday and sent condolences to the grieving families of the dead.

Chairman Senate of Pakistan Sanjrani deeply mourns the tragic loss of over 300 Pakistani lives in the recent boat accident off the coast of Greece, his office said in a tweet.

"With heavy hearts, we extend our heartfelt condolences to the grieving families during this time of immense sorrow and grief. Our thoughts and prayers are with you, and we pray that the departed souls find eternal peace," he said.

"This devastating incident underscores the urgent need to address and condemn the abhorrent act of illegal human trafficking," he said.

Pakistan's Foreign Office said on Saturday that 12 Pakistanis had been found alive as National Assembly Speaker Raja Pervaiz Ashraf urged the government to “immediately investigate” the incident.

The Greece boat tragedy has exposed the refugee crisis confronting the European Union as tens of thousands seek sanctuary from war, persecution and poverty.

The number of Pakistanis traversing dangerous routes to Europe in search of a better future has reverberated through the country, prompting Prime Minister Shehbaz Sharif to declare Monday a national day of mourning for those who died in the boat’s sinking.

Taking to Twitter on Sunday, Sharif ordered a “high-level inquiry” into the incident.

“I assure the nation that those found negligent towards their duty will be held to account. Responsibility will be fixed after the inquiry and heads will roll,” Sharif wrote.

Sharif also directed the Foreign Office to coordinate with Pakistani embassies abroad to take measures to capture the Pakistani human smugglers who operate from abroad. “Best efforts should be made for all Pakistanis. I will not tolerate any laziness and incompetence,” a statement quoted the prime minister as saying.

A top Federal Investigation Agency (FIA) official said at least 12 suspected human smugglers, including one who was trying to board a flight from the Karachi International Airport to Dubai, have been arrested since last Friday.

“These people are involved in luring and trying to smuggle Pakistanis illegally to Europe via the Middle East and Africa and some of them are also involved in sending Pakistanis on the boat which sank in Greece,” DIG Alam Shinwari said.

Shinwari said investigations had confirmed that 21 Pakistanis hailing from Khuiratta and Charhoi in Pakistan-occupied Kashmir were on the boat.

Another senior FIA official said some of the Pakistanis involved in human smuggling to Europe are based in Libya.

“They have sub-agents working for them in Pakistan who charge Rs 1 to 2 million and even more from each person to get them to Europe. They are first flown legally to the UAE and then moved to Egypt and Libya. From Libya, the illegal voyage begins through the Mediterranean Sea,” the official said.

The recent Greece boat tragedy is one of the worst in the Mediterranean Sea, according to the EU Commissioner for Home Affairs Ylva Johansson.

Every year, tens of thousands of migrants fleeing war, persecution, climate change and poverty risk treacherous routes to Europe.

Johansson condemned the role of “smugglers” who put people on the boats.

“They are not sending them to Europe, they are sending them to death. This is what they’re doing and it’s absolutely necessary to prevent it,” she was quoted as saying by CNN.

Despite the dangers, tens of thousands of people are willing to risk everything to make the unsafe journey to Europe, searching for a better life.

Separately, the Human Rights Commission of Pakistan (HRCP) on Monday asked the state to take responsibility “for its part” in the Greece boat tragedy.

Expressing shock and grief, it said that the incident should serve as a “stark reminder to the state that it has failed to stem a longstanding and grievous human rights violation”.

Pakistan is a well-known source, transit and destination country for trafficking in persons. However, it is clear that a serious lack of coordination among law enforcement agencies continues to allow traffickers to operate with impunity,” it said.

It highlighted that the government must “acknowledge that the dearth of economic opportunities available in the country compels more and more people to take their chances on such routes without being aware of the risk”.

“The state must also implement comprehensive anti-trafficking legislation and train the public officials concerned to identify and report such crimes and hold the perpetrators to account,” it added.

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