Around 230 partygoers were rounded up for drinking and dancing by police in Iran, according to the official Iranian Students' News Agency (ISNA).
In a double swoop officers picked up 140 revellers, a mixture of boys and girls, at a secret party in a garden on the outskirts of the capital Tehran, and nabbed another 90 at another location inside the city last night (21 December).
Drinking alcohol and mixed parties of unrelated men and women are illegal and considered a sin under Islamic law in Iran.
The parties were in celebration of the ancient Persian ritual called Yalda Night, the longest night of the year in the Northern Hemisphere.
The annual winter ceremony celebrates the renewal of the sun and the victory of light over darkness.
The ISNA report said some of the partygoers posted an invitation to others to join on Instagram, which led to police being alerted and making arrests.
Alcohol and drugs were confiscated at both scenes, the report said.
Cultural restrictions such as these are a regular feature of Iranian life since the 1979 Islamic revolution. The state's morality police roam the streets, and have the right to arrest women who do not wear a hijab and detain men with unconventional hairstyles.