Pakistan's new government has allowed a ban on the death penalty to expire, in a move condemned as "shocking and retrograde" by London-based rights group Amnesty International.

A presidential order imposing a moratorium on the implementation of the capital punishment, issued in 2008, expired on June 30.

Under the previous government led by the Pakistan People's Party (PPP), no one except a soldier convicted by court martial was put to death since 2008.

The PPP suffered a crushing defeat in elections on May 11, which swept to power the centre-right Pakistan Muslim League-N (PML-N) under Prime Minister Nawaz Sharif.

In Pakistan, all executions must be approved by the president. The PPP's Asif Ali Zardari is due to step down in August and the parliament controlled by the PML-N will elect a new head of state.

"The new government has decided to deal with all cases of execution on merit," the interior ministry spokesman Umer Hameed told the AFP news agency.

"The government has given clear instructions to see all such cases on a case-by-case basis and there will be no general amnesty for the convicts waiting for execution."

'Special category'

The interior ministry spokesman said up to 450 convicts were awaiting execution and their cases would be examined, adding that the government would show sympathy towards convicts who fell into a "special category" such as women and the elderly.

In a statement this week in response to rumours ahead of the decision, Amnesty International said, "As long as the death penalty is in place, the risk of executing innocent people can never be eliminated," 

"The systemic fair trials violations in Pakistan not only exacerbate this risk, but also put Pakistan in breach of its international obligations," Amnesty said, calling a possible decision "shocking and retrograde".

Many of Pakistan's crowded prisons lack basic facilities for inmates and the country often deals harshly with prisoners.

It also suffers daily attacks blamed on armed men linked to the Taliban and al-Qaeda, as well as chronic crime in its largest cities.

Various Pakistani officials have said that capital punishment is key for deterring crime in the country.