Islamabad , Pakistan ( CNN ) -- Pakistani Prime Minister Nawaz Sharif is vowing to stay put despite protests against his government that have enveloped the nation 's capital . On Saturday , police fired tear gas on protesters after thousands of them threatened to march on the Prime Minister 's house in Islamabad . At least 158 people were admitted to the Pakistan Institute of Medical Sciences , the hospital said . A 24-year-old man was in critical condition after being hit in the head by a rubber bullet . After failing to negotiate a solution with the protest movements , Sharif on Thursday asked the country 's powerful military for help brokering an end to the crisis . `` Tear gas is a normal practice undertaken all over the world to disperse a crowd . It is something that is an alternative to using force , '' Pakistan Defense Minister Khwaja Asif told CNN . `` The situation had precipitated to a point that if action had not been taken then it would have been a free fall for the government . '' At least 8,000 people have rallied in the city 's center after allegations of vote-rigging during last year 's election . Negotiations between Sharif 's government and his opponents , some of whom are calling for his resignation , have reached an impasse . Sharif announced in a statement on Saturday that he will not resign -- a demand he has called `` unconstitutional . '' Leading the two week-long protests are Imran Khan -- an enigmatic former cricket star who leads one of Pakistan 's largest political parties -- and outspoken cleric Tahir ul Qadri , an outspoken cleric who wants to overhaul the country 's political system . Khan is demanding new elections , while Qadri is demanding much more sweeping reforms . As the protests have grown in size and scope , the army has stationed personnel at government buildings in case protesters try to occupy them . A spokesman for Qadri said that protests tried to enter the road leading to the Prime Minister 's residence . Asif said that no decision had been made on whether to arrest Khan or Qadri . `` They violated their original commitment with the government to protest in a designated space like it is done in civilized countries , '' Asif said . `` We can not trust them . '' CNN 's Sophia Saifi reported from Islamabad and Joshua Berlinger reported and wrote from Atlanta . Journalist Adeel Raja in Islamabad contributed to this report .
Police fire tear gas after thousands of protesters threaten to march on PM 's house . Nawaz Sharif said in a statement that he wo n't resign . Protesters have been in Islamabad for the last two weeks .