Authorities have been steadily arresting a top tier of leadership in the moderate camp associated with Mir Hossein Moussavi, who placed a distant second in the June-12 presidential elections and has since emerged as the head of the mass protest movement that has taken to Iran’s streets over the past 10 days. A large group of clerics and politicians supports Moussavi, among them reformist former president Mohammad Khatami. But since June 13, many of Khatami’s leading associates have been detained, according to a website run by expatriate Iranians.

The crackdown may be spilling over into the powerful oil ministry, responsible for the lion’s share of the nation’s revenue. Deputy oil minister Akbar Torkan was replaced on Monday, apparently for political reasons, Reuters reported. Beyond that, opposition newspapers in Iran reported Tuesday that four of the six soccer players on the national team who had worn green arm bands in solidarity with the protesters had been dismissed.

On the diplomatic front, Prime Minister Gordon Brown of Britain announced Tuesday that his country had expelled two Iranian diplomats, a response to Tehran’s expulsion of two British diplomats on Monday.