David Cameron wants the West to contribute to rebuilding Georgia
Conservative leader David Cameron has said it is important the West shows solidarity with Georgia, as he visits the country's capital, Tbilisi.
He travelled to the region for talks with political leaders amid continuing tensions between Georgia and Russia.
"What Russia destroys, the EU and Nato will help... restore," said Mr Cameron.
Meanwhile, Foreign Secretary David Miliband said "Russian aggression" and threats to neighbouring states, such as Poland, were "unacceptable".
In a statement, Mr Miliband welcomed the signing of the Georgian ceasefire agreement by Russian President Dmitry Medvedev.
"The priority now is to ensure that the commitments made in the agreement are speedily and fully implemented," he said.
"There must be a complete and immediate withdrawal of Russian troops to the line they occupied before military action started."
Mr Miliband also condemned threats by Russian military figures to launch a nuclear strike against Poland if it allowed America to put a missile defence system on its soil.
The conflict began when Georgia attacked the breakaway region of South Ossetia a week ago, sparking Russian intervention. Its troops continue to occupy positions in Georgia.
Scores of people have died and thousands displaced since the fighting began.
David Cameron said a "clear message" needed to go out from the West
Speaking from Tbilisi, Mr Cameron said: "Just a few miles away there are still Russian troops on the ground, still doing damage."
A "clear message" needed to go out from all Western politicians - in government or opposition - that they would rally round Georgia and help rebuild it.
"This is a free, independent, sovereign democracy, whose borders and boundaries and legitimate sovereignty should be respected," Mr Cameron added.
Mr Cameron said it was vital checks were kept on all the armed groups in the area.
"What I've heard is there's a real danger that the militias that are in the areas that the Russians occupy may well be carrying out appalling atrocities.
"Reports are beginning to come in, obviously we need the evidence, but a very clear message needs to go out to the Russians that while they are in control of this territory - which they shouldn't be - anything that happens there is their responsibility.
"If atrocities have taken place, they will be held to account for that."
Mr Cameron earlier called for Nato to speed up Georgia's application for membership, in a bid to deter further attacks.
He has also called for Russia to be expelled from the G8 and for tough new visa restrictions to be placed on Russian nationals travelling to the UK.
The Liberal Democrats have urged the EU and others to "show tough resolve in helping to negotiate a lasting peace".
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