Residents of Portland, Oregon, are being confronted by hundreds of dildos as they go about their daily business after anonymous pranksters flung the phallic sex toys over power lines across the city.

The multitude of colourful dildos is being met, for the most part, with a wry smile and laughter in liberal Oregon.

Locals have taken to social media to post hundreds of pictures of the sex toys and to discuss who might be throwing them onto the lines.

In a burst of blue humour one group has discussed an appropriate moniker for the tricksters.

portland oregon is on a high dildo alert pic.twitter.com/LI5TxruB5R July 12, 2015

The sex toys have appeared over public streets, intersections and even a local market.

The number of dildos appears to growing. One commenter posted online: "There were only two dildos on the lines when I was there.

"Run for the hills, they're multiplying."

Another said: "I am loving this dildo thing. It is just hilarious and fabulous."

The dildos appear to have been hoisted in the same way people throw their shoes onto power lines, using a pair for a counter-weight.

Apparently the new trend in #Portland #Oregon is to throw dildos up on power lines. Wtf?! #KeepPortlandWeird pic.twitter.com/qNINxmolEt — Cody Perez (@Cody_Perez) July 8, 2015

A spokesman for public utility Portland General Electric told Reuters news agency he did not believe the rubber products posed a fire hazard.

Portland resident Lucila Cejas Epple told the news agency that she first encountered the dildos at a neighbourhood street fair over the weekend.

"You could spot them in several intersections and you could see all sorts of reactions to them," she said. "Some would blush, others would laugh, and most would take photos."