Karachi (AFP) - Pakistan on Thursday executed three Baluch separatists convicted of hijacking a plane in 1998, which they attempted to fly to India to disrupt Islamabad's first nuclear tests, officials said.

The executions were carried out on the 17th anniversary of the tests, which made Pakistan the world's seventh nuclear-armed power -- a landmark event for the impoverished Muslim country of 200 million people.

Two of the men, Shahsawar Baluch and Sabir Baluch were hanged in Hyderabad prison in southern Sindh province while the third, Shabir Rind, was hanged in Karachi, officials at both the prisons told AFP.

The trio were sentenced to death for hijacking a Pakistan International Airlines aircraft with 30 passengers on board on 24th May 1998, four days before the country's first nuclear test.

The flight took off from the port town of Gwadar in Baluchistan and was set to land in the southern port city of Karachi when the men stormed the cockpit and tried to force the pilot to fly to India.

But he instead flew to Hyderabad city, 160 kilometres (100 miles) north east of Karachi, tricking the hijackers into thinking that they were in India.

The next day Pakistani army commandoes overpowered all the three hijackers in a night operation.

Officials said the executed hijackers were Baluch nationalists who were demanding greater autonomy for they resource-rich but impoverished province.

At the time of the hijacking, officials said that one of the hijackers' demands was for Pakistan not to carry out the nuclear tests which were to due to be carried out in Baluchistan.

Pakistan went on to carry out five underground tests in the Baluchistan desert on 28 May 1998, in response to arch-rival India's second nuclear tests earlier in the month.

Separately on Thursday, a fourth hanging was also carried out, in Karachi jail, the prison official said.

The executed man, Mahmood Ali, had been awarded the death sentence for murdering a three-year-old child in 2003.

A moratorium on the death penalty had been in force in Pakistan since 2008, but executions resumed last December after Taliban militants gunned down 154 people, most of them children, at a school in the restive northwest.

The moratorium was initially lifted only for those convicted of terrorism offences, but in March was extended to cover all capital offences.

Before Thursday's executions, the number of people executed since the moratorium was lifted stood at 128.