The strength of protests shaking Iran was unclear on Thursday after a week of unrest that killed at least 21 people, with fewer reports of demonstrations as government supporters again took to the streets.

The Associated Press

TEHRAN, Iran — The strength of protests shaking Iran was unclear on Thursday after a week of unrest that killed at least 21 people, with fewer reports of demonstrations as government supporters again took to the streets.

It wasn’t immediately clear if the drop in reports of new demonstrations challenging Iran’s theocratic government meant the protests are subsiding or that the authorities’ blocking of social media apps has stopped protesters from offering new images of rallies.

Meanwhile, the Trump administration acknowledged the speed and breadth of the protests took both it and the Iranian government by surprise.

The past week’s protests have been the largest since the disputed 2009 presidential election, which ended in bloodshed. While many Iranians denounce the violence that has accompanied some demonstrations, they echo the protesters’ frustration over the weak economy and official corruption.

Thousands rallied on Thursday in support of the government in various towns and cities, including in the northeastern city of Mashhad, where the protests began last week and extended to other cities.

State television repeatedly broadcast nationalistic songs and described the pro-government rallies as an “answer to rioters and supporters to the riot.” That appeared to be a reference to President Donald Trump who tweeted in support to anti-government rallies.

The TV also broadcast footage of similar pro-government gatherings Thursday in the cities of Shiraz, Isfahan, Ardabil, Birjand and Yasuj.

In a letter Wednesday to United Nations officials, Iranian Ambassador Gholamali Khoshroo complained that Washington was intervening “in a grotesque way in Iran’s internal affairs.” He said Trump and Vice President Mike Pence were personally stirring up trouble.

“The president and vice-president of the United States, in their numerous absurd tweets, incited Iranians to engage in disruptive acts,” the ambassador wrote to the U.N. Security Council president and U.N. Secretary-General Antonio Guterres.

Trump’s U.N. envoy, Ambassador Nikki Haley, has called for an emergency Security Council meeting on Iran, saying the U.N. needed to speak out in support of the protesters. As yet, no meeting has been scheduled.

Late Wednesday, senior Trump administration officials acknowledged their surprise that the protests took hold so quickly.

“This was not on our radar,” said one official, who like the others spoke on condition of anonymity to discuss intelligence matters.

The officials said they believed conservative opponents of Iranian President Hassan Rouhani, a relative moderate within Iran’s clerically overseen government, started the demonstrations in Mashhad, but quickly lost control of them. That largely mirrors analysts’ beliefs.

The officials also said internet suppression by Iranian authorities made it difficult for protesters to publish their videos, with an upload sometimes taking the entire day. They said the U.S. government is still looking at its options at helping open up the internet, though no decision has been taken yet.