An earthquake was felt in the Iranian capital Tehran, sending hundreds of people running out onto the streets.
The quake measuring 5.2 magnitude struck shortly before 11:30 pm (local time) yesterday, according to the seismological centre of the University of Tehran.
The epicentre of the tremor was located about 40 kilometres west of the capital.
Authorities have not yet identified any damage or casualties from the quake, the latest in a series to have rattled the Islamic republic.
"We are asking people to stay calm as the traffic itself could create problems," the Iranian Red Crescent's Mortza Redmare said on television.
Shortly before midnight, the situation in parts of the capital seemed to have returned to calm.
Iran sits atop several fault lines, and yesterday's quake is the latest in a series to have hit the country in little more than a week.
A 6.2-magnitude earthquake struck the southeastern province of Kerman on December 13, leaving at least 18 people injured but causing only minimal damage.
Located around 50 kilometres north of the provincial capital of Kerman, the quake was measured as magnitude 5.9 by the US Geological Survey.
On November 12, Kermanshah was hit by a major 7.3- magnitude quake that killed 620 people according to the latest toll provided Monday by Tasnim news agency.
Iran's worst quake in recent years was a 6.6-magnitude tremor that struck near Bam in 2003, decimating the ancient city and killing at least 31,000 people.
In 1990, a 7.4-magnitude quake in northern Iran killed 40,000 people, injured 300,000 and left half a million homeless, reducing dozens of towns and nearly 2,000 villages to rubble.