The annual event marked its fifth year with such a surge in interest from stressed young office workers and students that organizers held two nights of pillow fighting before Christmas Day and plan another for Dec 30.

"Nowadays there are many white collar workers and students that are facing huge pressures at work and at school, so we hope to give them an outlet to release their stress before the end of the year," said Eleven Wang, the founder and mastermind behind the epic pillow fights.

"Sometimes we have pressure on us by our bosses, teachers and exams, so today we can go crazy. Everyone will get to write onto the pillows the names of their bosses, teachers and exam subjects, and enjoy and vent to the maximum," he added.

"After releasing the stress, we can once again face our daily life with joy."

Pillows were handed out at the door as participants entered, then emotion stoked by a rock concert, with many on the floor of the huge event space rocking and waving their pillows in time to the music.

Then came the fighting.

Pillows filled the air, with many combatants opting for throwing rather than using them to whack opponents. A few hapless participants shielded their heads with as many pillows as they could hold, but most ventured eagerly in to the fray.

"I really enjoyed the fight, but my friend was useless. He joined in for two ticks and could not go on, he was afraid of getting beaten by other people," said 24-year-old Chen Yi.

"I thought it was pretty meaningful. I've just been working so much (at the office) and never get to break out in a sweat, so it felt really good."

Others gamely said they enjoyed the experience even though they ended up as attackees rather than attackers.

"I don't know who pushed me, but all of a sudden I was in the pile of pillows, where I became the target of many people, and was beaten by all sorts of people," said university student Zhu Shishan. "Very meaningful."

(Reporting by Shanghai Newsroom; Editing by Elaine Lies)

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