Pakistan has dismissed as "ridiculous" claims by a banned Baloch separatist outfit of carrying out the deadly blast in a fruit market here that killed at least 24 people.
Initial probe has indicated that United Balochistan Army (UBA) - a lesser-known separatist outfit operating in the restive southwest province - has no links to the bomb attack, the Interior Ministry said in a statement issued late last night.
Mureed Baloch, a spokesman for the UBA, told reporters in Quetta last evening that his organisation was behind yesterday's bomb attack in the fruit market that claimed at least 24 lives.
"Our organisation has carried out the bomb attack in fruit and vegetable market in the twin city in reaction to operations conducted by security forces in Kalat, Turbat, Panjgur, Mastung and other parts of Balochistan," he said.
The UBA had also claimed responsibility for the Jaffar Express bomb blast in Sibbi on Tuesday that killed 17 people.
However, the Interior Ministry rejected UBA's claims.
"Accepting responsibility for the attack by this organisation is not just surprising, but also ridiculous," the Ministry's spokesperson said.
He said an investigation by intelligence and security agencies had indicated that the blast had roots "somewhere else".
"Those responsible for it will be chased after completion of the investigation," he said, without identifying who they suspected.
The blast yesterday came merely over a month after the attack on the District and Sessions Court here in which 11 people, including a judge, were killed.
In the past three years, no major terrorist attack took place in Islamabad, considered to be the safest city in Pakistan that has been wrecked by violence for over a decade.
However, the city did witness bloodshed but most of it was due to targeted killings.
In the early months of 2011, the capital was shaken by the assassination of senior government officials such as then Punjab governor Salman Taseer and Federal Cabinet member Shahbaz Bhatti.
Last year, Chaudhry Zulfikar, the prosecutor in Benazir Bhutto's assassination case besides the Mumbai case, was gunned down in the city while a senior member of the Haqqani clan was also shot dead in the federal capital.
The deadliest terror attack in Islamabad was the suicide attack on Marriott Hotel in 2008 that left 60 dead and 262 injured.