Pakistan's newly formed parliament elected Shehbaz Sharif on Sunday as prime minister for a second time, Geo TV reported, three weeks after uncertain national elections caused delays in the formation of a coalition government.

Voters in Pakistan went to the polls on Feb. 8 in an election marred by a mobile internet shutdown, arrests and violence in its build-up and unusually delayed results, leading to accusations that the vote was rigged.

Sharif returned to the role he held until August when parliament was dissolved ahead of the elections and a caretaker government took over.

The vote in parliament, which first met on Thursday, took place amidst tight security as candidates backed by former jailed premier Imran Khan have protested against the result and called for his release.

The Sunni Ittehad Council (SIC) party backed by Khan alleges that the national election was rigged against them and has called for an audit of the polls. No single party won a majority.

Sharif, 72, is the younger brother of three-time Prime Minister Nawaz Sharif, who spearheaded their Pakistan Muslim League-Nawaz (PML-N) party's election campaign.

Candidates backed by Khan gained the most seats but the PML-N and the Pakistan Peoples Party (PPP) agreed to form a coalition government, which enabled Shehbaz Sharif to be elected as prime minister as his brother stepped aside.

In his previous term, Sharif's government was able to negotiate a critical International Monetary Fund (IMF) deal but the process was mired in challenges, and measures required by the agreement - which expires in April - have contributed to rising prices and added pressure on poor and middle class households.

The new government will have to immediately start talks with the IMF for the next agreement to shore up the country's economy whilst also dealing with growing discontent over deepening poverty.

The government will also have to grapple with ongoing challenges from Khan's supporters.

(Reporting by Charlotte Greenfield and Ariba Shahid; Editing by Raju Gopalakrishnan and Miral Fahmy)