ISLAMABAD, Pakistan (CNN) -- Two students at the Red Mosque in Islamabad who tried to surrender Friday were shot dead by radical Islamic students, intelligence sources in Pakistan said.
A view of bullet-riddled besieged radical Islamic Red Mosque in Islamabad, July 6, 2007.
The sources gave no additional details of how the shootings occurred. CNN is attempting to reach officials inside the Red Mosque for comment.
Pakistani forces and radical Islamic students in Islamabad -- Pakistan's capital -- remained locked in a tense standoff at the Lal Masjid, or Red Mosque, punctuated by heavy explosions and periodic exchanges of gunfire, a four day siege that has now resulted in at least 26 deaths.
The violence began Tuesday when about 150 militant students attacked a police checkpoint close to the mosque. Police fired tear gas and the students fought back with sticks and guns and took refuge in the mosque.
The government said Friday talks were over with the students.
"There will be no more dialogue," said Deputy Information Minister Tariq Azim. "It has to be an absolutely total surrender, unconditional total surrender."
Pakistani forces and the students exchanged periodic gunfire early Friday that was punctuated by heavy explosions.
The Pakistani government refused to meet a demand by those inside the controversial mosque that they be allowed to surrender without facing arrest. Watch as the mosque standoff continues »
Intelligence sources say the nearly 1,000 people who remain holed up inside the mosque are facing a food and water shortage that is making living conditions inside miserable.
At least 50 of those people are well-armed hard-liners, according to Interior Minister Aftab Ahmed Khan Sherpao.
Maulana Abdul Aziz, the top cleric of the Red Mosque, joined the government's call for the students to surrender, a day after he was arrested trying to slip out of the mosque disguised in a burqa -- the head-to-toe covering worn by some Muslim women.
More than 1,200 of the students have already surrendered, although less than 10 have done so since early Thursday. Aziz told state-run TV that about 850 students remained inside -- including children, around 600 women and some 14 men armed with Kalashnikov sub-machine guns.
Brigadier Gen. Tareen of the Pakistan Rangers, head of the military operation at the mosque, said the older students inside were using young boys and girls as human shields.
"We will establish writ of the government at any cost, and these people don't have any other choice other than to surrender," he said.
Pakistani forces have demolished the Red Mosque's front walls and warned students by loudspeaker they had one last chance to surrender before a full attack took place, intelligence and military sources told CNN.
At least 24 people, including two members of the security forces and one journalist, have been killed in the two days of battles.
Tensions have been simmering between police and the students at the mosque, who are blamed for a string of recent kidnappings of civilians, Chinese nationals and Pakistani police. The government has been investigating the activities of the mosque, whose students are demanding sharia, or Islamic law, be instituted in Islamabad.
As part of the clampdown on the mosque compound -- which includes several madrassas, or religious schools -- police set up a security perimeter around the area last week.
The violence began Tuesday when about 150 militant students attacked a police checkpoint close to the mosque. Police fired tear gas, and the students fought back with sticks and guns.
Pakistan President Pervez Musharraf earlier announced he would give 5,000 rupees ($83) to any student who surrendered.
The Pakistan Rangers, a paramilitary group, are conducting the operation with the help of the police and the army. The area around the mosque is totally sealed, and nobody is allowed to enter or leave. E-mail to a friend
CNN's Syed Mohsin Naqvi contributed to this report.