The anniversary of Iran's Islamic revolution has traditionally been an time for the country's leaders and people to demonstrate support for the government.
Thirty-one years ago, communist, nationalist and Islamic parties united to oust Mohammad-Reza Shah Pahlavi, a ruler they criticsed for being pro-Western and despotic.
After he was sent into exile, the Islamic republic was formed and a new government was brought in under the leadership of Ayatollah Ruhollah Khomeini.
Last year's disputed presidential election, however, has highlighted significant political divisions in the country and sparked widespread opposition protests.
In the past eight months, Iran has seen some of the most violent clashes between the people and the government since the 1979 revolution.
What was supposed to be a time of festivities for Iran, has been overshadowed by rising tensions as opposition groups have threatened to use the anniversary for anti-government demonstrations.
Al Jazeera's Nazanin Sadri reports.
Source: Al Jazeera