The United Nations has urged Tehran to curb its use of force against demonstrators and restore Internet service amid a wave of protests sparked by a hike in gas prices across Iran that has left at least a dozen people dead.

Speaking to reporters in Geneva on November 19, UN human rights spokesman Rupert Colville voiced deep concern at the Iranian security forces' use of live ammunition in clashes with protesters and called the extent of casualties 'clearly very serious.'

Iranian officials say 12 protesters and members of Iran's security forces have died and that more than 600 people have been arrested since the protests erupted on November 15, when the government announced it was rationing gasoline purchases and cutting subsidies amid biting U.S. sanctions imposed after President Donald Trump unilaterally withdrew the United States from a 2015 nuclear agreement.

However, Colville cited reports suggesting that the actual number of people killed was in the dozens.

Earlier in the day, judiciary spokesman Gholamhossein Esmaili said that 'calm has been restored in the country,' but the situation on the streets remains unclear largely due to an Internet shutdown imposed by the authorities.

Videos posted on social media in defiance of a near total Internet outage appeared to show overnight protests in several cities and a heavy presence of security forces in the streets.

The authenticity of the images could not be verified.

WATCH: Several people have been killed in Iran after four days of violent protests over a spike in gasoline prices.

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