http://www.bbc.co.uk/news/world-europe-19684708 party invitation which went viral on Facebook ended in rioting and injury after thousands of revellers descended on a small town in the Netherlands.
Haren had been braced for trouble all week after what should have been an invite to a small-scale celebration was passed on to 30,000 people.
The girl whose 16th birthday was being celebrated had not set her Facebook event to "private".
Riot police broke up crowds of revellers who flocked to the town.
The girl who issued the invitation fled her home on Friday, hours before at least 3,000 people turned up in Haren - a town of just under 19,000 near the city of Groningen.
Up to 600 riot police were deployed "She posted the invitation on Facebook and sent it to friends, who then sent it to other friends and soon it spread like wildfire across the internet," Groningen police spokeswoman Melanie Zwama told AFP news agency.
Hundreds of riot police were deployed to control the crowds and they were pelted with bottles and stones, as well as flower pots even bicycles, the Dutch news agency ANP reports.
At least six people were hurt and 20 arrests were made as rioters vandalised and looted shops, setting a car on fire and damaging street signs and lamp-posts, according to Reuters news agency.
Among the crowds could be seen revellers wearing T-shirts marked "Project X Haren" after Project X - a film released earlier this year about a party which grows out of control.
Some revellers accused the police of over-reacting.
A new Facebook page has since been created called "Project Clean-X Haren" to clear up after Friday night's disturbances. It had more than 17,000 "likes" as of Saturday morning.
