Iranians protesting soaring food prices launched a spontaneous three-day boycott of milk and bread purchases, in a sign that growing economic hardship could lead to more civil disobedience.

The grass-roots campaign, which ran from Saturday through Monday, wasn't affiliated with any opposition group. Dozens of Iranians said in interviews and on social-networking sites and blogs that they had participated in the boycott, and a number of bakeries and grocery stores across Tehran, the capital, reported declines in milk and bread sales of as much as 90%...

Members of Iranian opposition groups say that though they didn't organize the campaign, they are studying it to see if such movements could serve as a platform for broader action in the future targeting the regime and entities owned by the government.