* Anti-government protests have lasted two weeks
* Prime Minister Nawaz Sharif says will not resign
* Talks between government, opposition have failed repeatedly (Updates with protest, Qadri quotes, details)
By Maria Golovnina and Mehreen Zahra-Malik
ISLAMABAD, Aug 28 (Reuters) - A major protest day that Pakistan's opposition termed decisive drew to a close on Thursday evening with thousands of activists still massed outside parliament demanding that Prime Minister Nawaz Sharif resign.
At least 10,000 people, some armed with sticks, crowded Islamabad's so-called Red Zone, where parliament, the prime minister's residence and embassies are located. The area was heavily littered with rubbish and reeked of human waste.
Security forces sealed off the protest site in case the crowd tried to storm nearby government buildings - which local media said had been evacuated - or clash with police.
Sharif, who met the country's powerful army chief earlier in the day, flew to the city of Lahore - his political powerbase - for a funeral but was expected back later Thursday night.
The future of the protest ultimately depends on the position of the army in a coup-prone country ruled by the military for half of its history.
Some officials have accused the army itself of orchestrating the protests, but so far the army has been neutral and called for restraint.
The prime minister has asked army chief General Raheel Sharif to "play his role" in resolving the conflict, a military source told Reuters, but it was not clear exactly what he was expected to do.
"All stakeholders have been requested to negotiating table to resolve the issue ... but it's just the beginning," the source said.
Pakistan has been gripped by mass rallies for two weeks, with thousands of protesters led by cricketer-turned-politician Imran Khan and cleric Tahir ul-Qadri camped outside parliament demanding Sharif's resignation.
"The government is unconstitutional, it must go. We want a national government formed for democratic reform," Qadri said told the flag-waving crowd in a passionate speech.
His camp had earlier said the crowds would soon be free to leave as the government had not met their demands, but police later complied with one of them by registering a murder case in the killing of 14 activists at a protest in June, a lawyer said.
Qadri dismissed the move, saying the wording of the document did not satisfy him, and gave the cheering crowd no advice on what to do next. Some defiant protesters have dug graves at the site to show they are ready to die for their cause.
OPPOSITION PRESSES ON
Pakistan, a nuclear-armed nation of 180 million, has swung between democracy and military rule for decades and the army's position is key to what happens next.
Few expect the army to try to grab power again. It has stayed out of the stand-off, providing security for Sharif and key government installations and calling on all sides to show restraint and solve the dispute through political means.
But even if protests do eventually lose steam, observers expect Sharif will still emerge significantly weakened from the crisis, with the army likely to further sideline him on security and foreign policy issues.
A departure of Qadri's highly organised supporters from the area in the heart of the capital would undercut Khan's efforts to breathe new life into his movement, which has drawn far fewer people than his original goal of a million-people march.
Khan declared he would not abandon his demands. "I will not leave here. I will not accept this monarchy. I want real democracy," he told his supporters.
Qadri, who has a huge following and runs a network of Islamic schools and hospitals, had said Thursday would be "Revolution Day".
The demonstrations come at a difficult time for Pakistan, already plagued by an Islamist insurgency, sectarian tension and recurrent power shortages. Many Pakistanis are deeply unhappy with the government's performance since it came to power after winning an election in May last year. (Additional reporting by Mubasher Bukhari in Lahore and Sheree Sardar in Islamabad; Writing by Maria Golovnina; Editing by Tom Heneghan)
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