Mobile internet access has been restricted in several Iran provinces, an Iranian news agency reports, a day before new protests are expected to kick off.
Social media posts, along with some relatives of people killed in unrest last month, have called for renewed protests and ceremonies to commemorate the dead to be held on Thursday.
State media, meanwhile, said intelligence ministry agents had seized a cache of 126 mostly US-made guns smuggled to the central city of Isfahan from abroad.
The protests were initially sparked in November by petrol price hikes but demonstrators quickly expanded their demands to cover calls for more political freedom and other issues.
The government, which launched the bloodiest crackdown on demonstrators in the 40-year history of the Islamic Republic, blamed foreign enemies for stoking tensions.
An official denied any order by the authorities to block the internet, which was shut down for about a week in the November unrest.
A news agency also cited mobile operators saying their services had not been disrupted.
However the semi-official news agency ILNA quoted an informed source at the Communications and Information Technology Ministry as saying mobile internet access to overseas sites was blocked by "security authorities" in Alborz, Kurdestan and Zanjan provinces in central and western Iran and Fars in the south.
"According to this source, it is possible that more provinces will be affected by the shutdown of mobile international connectivity," ILNA said.
Internet blockage observatory NetBlocks confirmed the blockages on Twitter.
"Confirmed: Evidence of mobile internet disruption in parts of Iran ... real-time network data show two distinct drops in connectivity this morning amid reports of regional outages; incident ongoing," NetBlocks posted.
The shutdown appeared to be spreading.
"I just checked myself and asked a friend, and the internet is off on our mobiles," a resident in Ahvaz, the capital of the oil-producing Khuzestan province, told Reuters.
But a communications ministry spokesman denied there was an order to shut down the internet.
Australian Associated Press