Pakistan declares day of mourning after bomb attacks kill over 130

Pakistan declared a day of mourning after two bombings killed over 130 people.

The deadliest of the two was a suicide bombing in city of Mastung that killed at least 128 people. 

Earlier in the day, a similar attack targeted the convoy of a local election candidate in the northwest city of Bannu. 

Pakistan heads to the polls on July 25 and the army says it will deploy 370,000 troops to ensure the elections are secure and fair. 

Shaking confidence in security just as the dramatic arrest of ex-prime minister Nawaz Sharif ratcheted political tensions higher ahead of nationwide polls.

Sharif's highly-anticipated return from London and subsequent arrest for corruption was overshadowed as the carnage in Mastung, in the southwest province of Balochistan, unfolded late Friday.

A week ago, Sharif was sentenced in abstentia to 10 years in prison on corruption charges. 

He was transferred to the garrison city of Rawalpindi, adjacent to Islamabad, after landing in Lahore Friday. 

Sharif claims he is the victim of a military conspiracy, and there are widespread allegations from the media, politicians and analysts that the powerful security establishment is meddling in the polls.

Mobile signals were blocked and police deployed in the eastern city of Lahore where Sharif's supporters had gathered as he landed.

Soon after, the scale of the destruction in Mastung, hundreds of kilometres to the southwest, where a Daesh suicide bomber had detonated at a crowded political rally, began to emerge.

Hospitals in the area have been placed under "emergency" management after being overwhelmed in the hours after the attack, with around 150 also wounded in the blast, many still in critical condition.

The attack was by far the deadliest of a series of blasts at various campaign events this week that have killed at least 154 people, including two local politicians, and underscored ongoing security challenges following years of optimism over improvements.

Violence has dropped significantly since the country's deadliest-ever militant attack, an assault on a school in the northwestern city of Peshawar in 2014 that left more than 150 people dead, mostly children.

The military intensified operations against militants in the tribal areas along the border with Afghanistan in the wake of that attack, and security has improved dramatically.

But analysts have long warned that Pakistan is not getting to the root causes of extremism, and that militants retain the ability to carry out spectacular attacks like the blast in Mastung.

Sharif has been banned from holding political office, but analysts have said his return is aimed at reinvigorating support for his party, now led by younger brother Shahbaz, which is limping towards the vote after a lacklustre campaign.

The military has already warned of a security threat in the run-up to the vote, and said it will deploy more than 370,000 soldiers on polling day.