The threat of Pakistan's angry young marchers

Preparations are under way in the capital to control the planned demonstrations

As Pakistani authorities brace themselves for two huge protest movements taking to the streets on Thursday, Pakistan's Independence Day, the BBC's M Ilyas Khan considers the implications of this assault on the leadership of Prime Minister Nawaz Sharif.

Just over a year after it won a landslide victory in elections, the government is coming under siege from two of the country's latest generation of politicians.

Neither of them began life as career politicians, but they now command vocal support and their angry rhetoric has the power to marshal equally angry crowds.

Although they are untested leaders, one year on from the election of Mr Sharif, they are posing questions about basic problems such as unemployment and the country's electricity supply.

One of them is Imran Khan, a former cricket hero who formed a political party in 1997 but has only recently hit a chord with the masses.

His Movement for Justice (PTI) party emerged as the second largest in terms of votes won in the 2013 elections, though it finished in third place in terms of the tally of parliament seats.

It trounced its opponents in the Khyber Pakhtunkhwa province, which it now rules.

Mass of frustration

Analysts say that to a growing chunk of the Pakistani youth - which makes up more than 50% of the national population - Mr Khan comes across as a possible saviour against what they see as "corrupt and inept" leaders.

Imran Khan wants to force Nawaz Sharif to step down with this latest protest

Their anger follows from their frustration over a sinking economy, the uncontrolled growth of militancy, and a system of service delivery that has nearly ground to a halt.

Mr Khan is now threatening to let loose this mass of anger and frustration on Islamabad unless the prime minister resigns and paves the way for early elections.

Mr Khan believes that last year's elections were rigged. He has chosen 14 August, Pakistan's Independence Day, to descend on Islamabad and stage a sit-in which he says will continue until the government falls.

Prime Minister Sharif's second detractor is Dr Tahirul Qadri, a firebrand cleric who lives in Canada and is known there and in the rest of the West as a Sufi religious scholar.

He acquired a taste for politics when the political arena opened up in 1989 after the death of military ruler General Zia. Ever since he moved to Canada, he has maintained seasonal migrations to Pakistan.

His Pakistan Peoples Movement (PAT) made little electoral impact when it was launched, and it is still in oblivion.

Tahirul Qadri holds great sway over many youth who look up to him in Pakistan

Youth's spiritual guide

But he has made up for his lack of mass appeal by building a support base of many tens of thousands of youthful men and women who have benefited from a country-wide chain of welfare and educational charities he set up in 1981.

These young people consider Mr Qadri their spiritual guide and mentor.

Analysts say they are Mr Qadri's captive audience, and can be as militant or as docile as the words Mr Qadri employs to motivate them.

Clashes between Mr Qadri's supporters and police have broken out in the past

Last year, more than 40,000 of them descended on Islamabad to "rid the people of corrupt rulers".

Nearly half of them braved the city's freezing cold winter and held on for three days on the central Jinnah Avenue, sleeping on the pavements and using the forested green areas on both sides as their open-air toilets.

They went back without dethroning the rulers. Instead, their leader ended the march by signing an agreement with those same rulers on political and electoral reforms. No-one ever took that agreement seriously.

These "captive" young men and women are once again ready to march on Islamabad, and this time they intend to join forces with Mr Khan's youth.

The government has requisitioned hundreds of shipping containers to be used as hurdles along the streets and highways between Lahore, the epicentre of the brewing storm, and Islamabad - a journey of nearly 400km (250 miles) - to inhibit or slow down the marchers' progress.

Some supporters of Prime Minsiter Nawaz Sharif have come out to condemn the planned march.

It has shown more accommodation towards Mr Khan - Prime Minister Sharif extended him an olive branch and invited him for a dialogue - than Mr Qadri.

Is it about Musharraf?

Government leaders in private conversations allege that Mr Qadri is not only an unelected political nobody, he may well be advancing the agenda of "certain forces" (elements within the military) that do not favour democracy.

Many in the government also view Mr Khan with suspicion.

They cite senior newspaper columnists who have in the past openly linked his political career to officials of the Pakistani army and its ISI intelligence service.

There are fears this might in fact be about a rescue plan for beleagured former ruler Pervez Musharraf

Also, a famous Pakistani social worker, Adus Sattar Edhi, in a TV interview some years ago accused Mr Khan and a former ISI general of planning to topple ex-Prime Minister Benazir Bhutto's government in 1996 and replacing it with a cabinet of technocrats.

Both Mr Qadri and Mr Khan have denied all these allegations.

But on Sunday, a senior leader of Mr Sharif's PML-N party, Raja Zafarul Haq, again reverted to this theme and accused the pair of planning to create anarchy so as to force the government to let former president and army chief, Pervez Musharraf, off the hook.

Nawaz Sharif appears determined to withstand the pressure, saying he will defend the people's mandate

Mr Musharraf has been under house arrest since last year. He became the first ever army chief in Pakistan to be indicted in a high treason case.

This has led to resentment within the military and caused tensions with Mr Sharif's civilian government.

Government officials now fear that Mr Qadri could hijack Mr Khan's show and start a confrontation with the law enforcement authorities.

In a country with a history of military coups, everyone fears that violence beyond a certain point may force the hand of even a reluctant army to intervene.