Posters begging Pakistan's powerful army chief to launch a coup appeared in major cities including the capital Islamabad overnight, raising eyebrows in a country that has been ruled by the military for more than half its history.

The posters, which also appeared in Lahore, Karachi and the garrison city of Rawalpindi as well as several army-run cantonment areas, were placed there by "Move on Pakistan", a largely-unknown political party founded in 2013.

"Talk of leaving has become old, for God's sake come now," scream the posters, referring to General Raheel Sharif's decision to step down at the end of his tenure this year.

They feature a large photograph of the mustachioed general.

"Dictatorship is much better than this corrupt government," Ali Hashmi, chief organiser behind Move on Pakistan, told AFP Tuesday.

"The way General Raheel Sharif has dealt with terrorism and corruption, there is no guarantee that the next man would be as effective as him," he said.

Prime Minister Nawaz Sharif is said to be preparing to name a successor to the wildly popular general, who is no relation and whose three-year tenure expires in November.

Widely credited with Pakistan's improved security situation, he is the frequent subject of hashtags such as #ThankYouRaheelSharif and #PakLovesGenRaheel.

The prime minister and his government, in contrast, have been plagued by accusations of corruption and inefficiency.

But, despite his popularity, the army chief's announcement in January that he would step down at the end of his tenure won him praise for respecting democratic institutions -- unlike three of his predecessors.

There was no immediate reaction to the posters from the military or the federal government.

Political analyst Hasan Askari said he did not foresee any threat to the current political system in Pakistan. "There cannot be an organised movement unless there is a popular sentiment present," he said, dismissing the posters.

Hashmi said that authorities in Islamabad and Punjab province, the prime minister's power base, had removed the posters -- but that they continue to attract attention in other provinces.

Military dictatorships have ruled Pakistan for more than half its 69-year history, and the armed forces are widely seen as controlling defence and foreign policy.

Whoever takes over Raheel Sharif's role will face an array of daunting challenges, including keeping homegrown militants in check, vexed relations with India and the role Pakistan wants to play in promoting peace in Afghanistan.