Violent clashes between anti-government protesters and the Turkish authorities are "disturbing and concerning", David Cameron has said.
But Mr Cameron was keen to stress that the nation was a friend of the United Kingdom and stopped short of any direct criticism about the way the demonstrators had been dealt with.
At a briefing for international journalists ahead of the G8 summit, he said: "What I would say is that I think that Turkey's journey over the last few decades in terms of political freedom and economic freedom has been remarkable, and has been very important for the stability of our world, and is something we should encourage and something I've talked about to prime minister Erdogan frequently. And we admire that progress.
"Obviously the events taking place in Istanbul are disturbing and concerning and what I'd say is that it's very important that everyone shows a proper sense of responsibility. And that is the view that I take about what needs to happen. But let me just reinforce the point that I do think Turkey's progress overall is something that other countries have quite rightly looked up to."
The unrest was sparked by a violent police crackdown on a peaceful sit-in by activists objecting to a project replacing a park with a replica Ottoman-era barracks.
Turkey's prime minister Recep Tayyip Erdogan has held talks with a group of activists to attempt to bring an end to the protests.
Mr Cameron added: "I think everyone in Britain has been watching the television over recent nights and has watched what has happened in Istanbul, and obviously that raises lots of concerns.
"We say this as friends of Turkey, as friends of the Turkish people, and obviously we want these things resolved. I note that prime minister Erdogan today, I think, is meeting with some of the protesters and we hope that that will go well but, as I say, we say this as a friend of the Turkish people, a friend of Turkey, we want - we want your country to go on succeeding.
"And, as I said earlier, that means I think everyone is going to have to fulfil their responsibilities."