For those working for the BBC Persian service, interference and harassment from the Iranian authorities has become a challenging fact of life.

I am hugely proud of how they deal with that relentless pressure, and their unswerving commitment to delivering high quality, impartial journalism.

They arguably have the most difficult jobs in the BBC. They carry them out with unstinting dedication and in the knowledge that their work makes a critical difference to the lives of millions who crave access to free and accurate information, in a part of the world where it is scarce and extremely precious.

In recent months, we have witnessed increased levels of intimidation alongside disturbing new tactics. This includes an attempt to put pressure on those who work for BBC Persian outside Iran, by targeting family members who still live inside the country.

We remain extremely concerned about these actions by the Iranian authorities and the latest case only serves to underline this.

Last week the sister of a BBC Persian member of staff was arrested. She was detained and held in solitary confinement on unspecified charges at Evin Prison in Tehran. Although she has now been released on bail, her treatment was utterly deplorable and we condemn it in the strongest possible terms.

It is just the latest in a campaign of bullying and harrassment by the Iranian authorities, putting pressure on the BBC for the impartial and balanced coverage of events in Iran and the wider region.

It follows the repeated jamming of international TV stations such as BBC Persian TV, preventing the Iranian people from accessing a vital source of free information.

In recent months a number of relatives of members of BBC Persian staff have been detained for short periods of time by the Iranian authorities and urged to get their relatives in London to either stop working for the BBC, or to "co-operate" with Iranian intelligence officials.

In other instances, passports of family members have been confiscated, preventing them from leaving Iran. This has left many BBC Persian staff too afraid to return to the country, even to visit sick or elderly relatives. Some have had their Facebook and email accounts hacked.

In addition, there has been a consistent stream of false and slanderous accusations against BBC Persian staff in the official Iranian media, ranging from allegations of serious sexual assault, drug trafficking, and criminal financial behaviour.

It has also included claims that staff have converted from Islam to Christianity or Baha'ism - potentially a capital offence in Iran as it is considered to be apostasy. This has put our staff, who in most cases left their families behind to come to London and work for the BBC, under immense pressure.

This issue is wider than the BBC - other international media face similar challenges. But it is behaviour that all people who believe in free and independent media should be deeply concerned about.

The BBC calls on the Iranian government to repudiate the actions of its officials.

We also ask governments and international regulatory bodies to put maximum pressure on Iran to desist in this campaign of intimidation, persistent censorship and a disturbing abuse of power.

Mark Thompson is BBC director general.

As the number of people accessing BBC News via mobile phones and tablet devices continues to grow, I'm pleased to report that we have just launched a new version of the BBC News app specifically aimed at large Android tablets. (There's already an app for iPad and smaller 7 inch Android devices.)

In an average week, the BBC News site and apps are currently visited by about 9.7m users worldwide, or about 26% of the total. There are more details here from our Product Manager for mobiles, Kate Milner.

Steve Herrmann is editor of the BBC News website.

It's become a tradition on the BBC News website that at the end of each year we look back at some of the faces that have been in the news, and in choosing a face for each month of the year we try to reflect a range of the different kinds of subjects that have been covered. We generally produce a list of women and a list of men, and since we regard it as part of our job to make the list interesting and engaging, we try to include some choices which are not obvious or predictable.

This, after all, is not a definitive list of the most important or influential people. It's not based on people's achievements, their popularity or their contribution to society. And it's not a celebration of either gender's role in humanity - it's just a selection of some of the faces from the headlines from the past year.

No one was more surprised than us, then, to see the phrase "pandagate" trending on Twitter on Wednesday, or the coverage in several newspapers on Thursday.

The inclusion on the list of Tian Tian, one of the pandas who arrived with such fanfare at Edinburgh Zoo, led some people to claim that we were not recognising the accomplishments of women. Tian Tian, being female, had been included in our list of women. However, as we pointed out yesterday, she was not the first non-human to be included on these lists - last year there was Peppa Pig who had got mixed up in a political wrangle. The year before there was Benson, a poisoned prize carp. Peppa was on the women's list, and Benson on the men's, though of course like Tian Tian they are not technically men or women.

One thing is at least clearer today. If Tian Tian hadn't justified her place on the list of newsmakers based on her arrival in Edinburgh, she would have done after this.

Giles Wilson is features editor of the BBC News website.