ST PETERSBURG, Russia (Reuters) -Russian President Vladimir Putin made the following comments at a plenary session of the St Petersburg International Economic Forum on Friday.

Putin spoke in Russian. The quotes were translated into English by Reuters.

ON UKRAINE:

"...I consider the Russian and Ukrainian people to be one people - in fact, in this sense, the whole of Ukraine is ours."

"We have such an ancient - it's not a saying, not a parable, but an ancient rule: where a Russian soldier's foot treads, it is ours."

"We, by the way have never questioned the right of Ukrainian people to independence and sovereignty. At the same time, the grounds on which Ukraine became independent and sovereign were laid out in the 1991 declaration of Ukraine's independence, it is clearly written in black and white that Ukraine is a non-aligned, non-nuclear, neutral state."

When asked what Russia's response would be if Ukraine used a dirty bomb, Putin said: "This would be a colossal mistake...maybe their last mistake...we always respond to all threats that are posed to us in a reciprocal way...Therefore, our response will be very rough and, most likely, catastrophic for the...regime, and unfortunately, for Ukraine itself. I hope it will never come to that."

ON ISRAEL-IRAN:

"In such cases, it is better not to get ahead of ourselves in order not to harm the process, but in my opinion, there are points of possible common ground. We are presenting our position to both sides. As you know, we are in contact with Israel and our Iranian friends.

"We are not seeking to mediate, we are just proposing ideas. And if they are attractive to both countries, we'll be happy about it...Now our proposals are also being discussed, we have contacts with our Iranian friends almost on a daily basis, so let's see."

ON HIS FEARS OF WORLD WAR THREE:

"It's worrying...What is happening in the Middle East, and of course, we are very concerned about what is happening around Iran's nuclear facilities."

ON IRAN'S BUSHEHR NUCLEAR PLANT:

"...We defend Iran's right to the peaceful atom...We have built a nuclear reactor in Iran, in Bushehr...And we, despite the complexity of the situation, despite the definite danger, we continue this work. We are not evacuating our personnel from there."

(Reporting by Reuters in St Petersburg, Moscow and London; Editing by Andrew Osborn)