(Photo: VCG)

Imran Khan's party said it has begun talks with independents and small parties to form a coalition government after a resounding triumph in Pakistan's general election, as rival parties planned protests over alleged vote rigging.

Khan's party Pakistan Tehreek-e-Insaf (PTI), or  Pakistan Movement for Justice, won 115 seats in Wednesday's ballot, short of the 137 needed for a simple majority.

The party has begun reaching out to potential coalition partners to form a government, according to spokesman Fawad Chaudhry, a task that analysts said should be straightforward.

"We have contacted small parties and independent members, they will soon meet party leaders in Islamabad," Chaudhry announced late Friday, adding that the process was likely to take about 10 days.

Chaudhry's comments followed an announcement by rival parties vowing to launch a protest "movement," after foreign observers voiced concerns about the contest.

More than a dozen parties calling themselves the All Parties Conference (APC) promised to protest over the results.

However, the group remained divided with some parties pledging to boycott joining the National Assembly and others calling for a new vote.

The outgoing Pakistan Muslim League-Nawaz (PML-N) party announced its support for the group but stopped short of saying it would boycott the new parliament.

And the Pakistan Peoples Party (PPP), which was notably absent from the APC, said in a separate announcement that it rejected the results, but vowed to try to convince the other parties to participate in the parliamentary process.

Khan, a former cricket star, will face myriad challenges, including militant extremism, an economic crisis with speculation that Pakistan will have to seek a bailout from the International Monetary Fund, water shortages and a booming population.