HARARE (Reuters) - Zimbabwean riot police used water cannon on Wednesday to scatter 20 activists protesting at the introduction of “bond notes”, a new domestic currency they say could touch off uncontrolled money printing and a return to hyperinflation.

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The Reserve Bank of Zimbabwe launched the notes on Monday with the goal of easing chronic cash shortages and supplement the dwindling U.S. dollars in circulation. Intelligence briefings seen by Reuters said if the notes’ value crashed, President Robert Mugabe’s 36-year grip on power could unravel.

In Harare, 20 youths from the opposition Movement for Democratic Change (MDC) tried to march through the streets waving placards saying “No to Bond Mugabe” and “No to fake money”, but were met by a phalanx of riot police.

Water cannon salvoes ensued, quickly dispersing the demonstrators. No arrests were reported.

Having failed to stop the launch of the bond notes, which many Zimbabweans fear will erode U.S. dollar savings, some people have tried to undermine the physical integrity of the $2 notes and $1 coins.

Mobile phone videos have circulated online of people rubbing the bright green $2 bond note against a sheet of white paper to leave a green smudge that they say demonstrates the poor quality of the ink and printing.

A Reuters experiment with a note also left green smears.

Critics in Zimbabwe’s small but vibrant social media community have pounced on the smudges as symbolic of the real value of the “bollars”. They are officially exchangeable at 1:1 to the U.S. dollar but many people believe they will quickly start to depreciate.

“We are currently witnessing one of the biggest scams in history ... Who just prints paper and determines its value?” tweeted ClaudeJrK.

The Reserve Bank has asked the public to report people who deface, disfigure or illegally exchange the bond notes.

Although it hopes the bond notes will ease shortages of cash, bank queues lengthened on Wednesday as workers and government employees sought to withdraw monthly salaries.

At independence from Britain in 1980, Zimbabwe was regarded as one of Africa’s most promising prospects. But its economy has nearly halved since 2000 after the violent seizure of white-owned commercial farms and disastrous printing of money.