Reports from Iran say several people have been detained for alleged links to the BBC's Persian service, which is banned in the country.
Mehr news agency said they were involved in newsgathering, recruiting and training for Iranian journalists and had arranged trips abroad for them.
A BBC statement said no BBC Persian staff members were working inside Iran.
It said the reports "should be of deep concern to all those who believe in a free and independent media".
Last week, the BBC accused the Iranian authorities of a campaign of bullying and harassment against those working for its Persian service.
'Anti-security crimes'
On Monday evening, a report by the semi-official Mehr agency cited an unnamed "knowledgeable source" as saying that "a number of people deceived by the lie-spreading BBC Persian network" had been arrested.
The source said they had "the mission of gathering news and information, producing content in various formats, recruiting, training and preparing for the departure of Iran's elite media workers from the country".
They had committed "many anti-security crimes as part of their co-operation with this network" since 2009, when mass protests erupted after the disputed re-election of President Mahmoud Ahmadinejad, the source added.
"The case of the detained people will be handed over to the judiciary department for the issuance of a verdict after the final compilation and preparation of the charges," the source stated, without naming them.
"As has been previously said, any kind of co-operation with the BBC Persian channel is illegal and will be prosecuted."
In a statement, the corporation reiterated that there were "no BBC Persian staff members or stringers working inside Iran".
"These latest reports appear to confirm our recent statements and should be of deep concern to all those who believe in a free and independent media," a spokesperson said.
"They admit that the Iranian authorities are engaged in a persistent campaign, intimidating and arresting people who they claim have connections with the BBC Persian service."
'New tactics'
In a blog published on Friday, the BBC's Director General Mark Thompson wrote that he had seen "disturbing new tactics", including the targeting of family members of Persian service staff working outside Iran.
Mr Thompson revealed that the sister of one man had been arrested the previous week and held in solitary confinement on unspecified charges at Evin Prison in the capital, Tehran.
"Although she has now been released on bail, her treatment was utterly deplorable and we condemn it in the strongest possible terms."
Mr Thompson also said some staff had had their Facebook and email accounts hacked, and been subjected to a "consistent stream of false and slanderous accusations... ranging from allegations of serious sexual assault, drug trafficking, and criminal financial behaviour".
In September, Iran arrested six film-makers, accusing them of working for BBC Persian. The corporation said they were independent, and that it had merely bought the rights to broadcast their documentaries.
Human Rights Watch said the harassment of BBC Persian staff was part of a wider campaign to stifle freedom of information in Iran ahead of parliamentary elections scheduled for next month.
It also comes amid mounting tensions over Iran's nuclear programme.
On Tuesday, Iranian media said MPs were considering a bill to prohibit the export of oil to the European Union, which approved a ban on Iranian oil imports last month in reaction to Tehran's continued refusal to halt uranium enrichment. The EU buys about 20% of Iran's oil exports.
