In the religious capital of Iran, the Islamic revolution still holds a powerful sway even as once-unthinkable signs of modernity creep into the city of Qom to challenge the faithful.

Iranian pilgrims at a Shiite holy site near the city of Qom intervened against the distribution of leaflets opposing Tehran's nuclear talks with world powers, state news agency IRNA reported Wednesday.

It said activists linked to the students' branch of the basij, Iran's Islamist volunteer militia, distributed the leaflets outside the Jamkaran mosque near the city in central Iran when several pilgrims stepped in to oppose their action.

Iranian President Hassan Rouhani, as decision time looms for a nuclear deal with world powers, sought Wednesday to win the support of the religious community at the "backbone" of the Islamic republic.

"For the government and the people of Iran, Qom is not a city, but the symbol of religious life," Rouhani, who faces criticism on the home front, said in a speech in the Shiite holy city of Qom.

Talks between Iran and six world powers in Istanbul on Tehran's nuclear program, the first in 15 months, began Saturday in a "positive atmosphere," a European Union spokesman said.

"There is a positive atmosphere. ... There is a desire for substantive progress," Michael Mann, spokesman for EU foreign policy chief Catherine Ashton, told reporters.

A stealth surveillance drone operated by the CIA penetrated deep inside Iran over three years ago, snapped images of Iran's secret nuclear facility at Qom and returned home, The Washington Post reported late Saturday.

The newspaper said that during that flight, analysts at the Central Intelligence Agency and other agencies watched carefully for any sign that the aircraft, called the RQ-170 Sentinel, had been detected by Tehran's air defenses on its maiden voyage.

Iran may be preparing to expand its nuclear program at an underground plant near the city of Qom, a diplomat has told the BBC, just days ahead of a visit by United Nations nuclear inspectors.

Iran appears to be poised to install thousands of new centrifuges at the underground site in the northern city, a Vienna-based diplomat told the British broadcaster late Friday.

The Special Tribunal for Lebanon probing the assassination of ex-Prime Minister Rafik Hariri is investigating Iran’s possible involvement in the Feb. 2005 bombing that killed Hariri and 22 others, the German Der Spiegel magazine reported on Monday.

The report said that there is evidence that link Iran with the murder of Hariri.