A group of Pakistani political parties has rejected the results of Wednesday's general election that looks poised to bring ex-cricketer Imran Khan to power.
Shahbaz Sharif (R), the younger brother of ousted Pakistani prime minister Nawaz Sharif and head of Pakistan Muslim League-Nawaz (PML-N), arrives with opposition leader Maulana Fazalur Rehman (L) for a press conference. Photo: AFP
Mr Khan's PTI party is ahead in the poll and has declared victory, but rival parties allege vote rigging.
After joint talks in Islamabad, one party leader said they would launch protests to demand fresh elections.
The rival parties include that of ex-PM Nawaz Sharif, which had earlier said it was ready to go into opposition.
PML-N leader Shahbaz Sharif, brother of Nawaz Sharif who is in jail on corruption charges, said the party had yet to decide whether or not to boycott parliament.
Sitting alongside him at a news conference, Maulana Fazalur Rehman, leader of the MMA party and spokesman for the group of rival parties, said: "We will run a movement for holding of elections again. There will be protests."
He added: "We will not allow democracy to be taken hostage by the establishment."
Leaders of more than a dozen parties had called the conference to form a joint strategy after the election.
What are the latest figures?
The election was seen as a contest between Mr Khan's Pakistan Tehreek-i-Insaf (PTI) party and Mr Sharif's Pakistan Muslim League-Nawaz (PML-N).
Results declared so far show Mr Khan's party is leading with 114 seats of the 272 National Assembly constituencies being contested, far ahead of the PML-N.
In third place is the Pakistan Peoples Party (PPP) led by Bilawal Bhutto Zardari, son of assassinated two-time prime minister Benazir Bhutto.
However a total of 137 seats is required for a majority and while Mr Khan is on course to become Pakistan's next prime minister, he will have to form a coalition government.
An official confirmation of the vote is still to come.
Were the elections fair?
Mr Khan, 65, has faced accusations that his campaign benefited from the backing of Pakistan's powerful military, a claim both he and the army deny.
On Friday, a European Union monitoring team said the election campaign featured a "lack of equality".
"Although there were several legal provisions aimed at ensuring a level playing field, we have concluded that there was a lack of equality and opportunity," chief observer Michael Gahler told reporters.
"Candidates with large political appeal and financial means - the so-called 'electables' - often dominated the campaign."
On Friday, the US expressed concern about "flaws" in the campaign process.
"These included constraints placed on freedoms of expression and association during the campaign period that were at odds with Pakistani authorities' stated goal of a fully fair and transparent election," the US State Department said.