LONDON (Reuters) - Only one in 20 Russian air strikes in Syria are aimed at Islamic State targets, Britain's defense secretary said on Saturday, warning that Vladimir Putin was instead killing civilians to shore up President Bashar al-Assad.
Russia earlier this week announced its decision to launch strikes on Syria, in a dramatic escalation of foreign involvement in a civil war more than four years old.
It bombed the country for a third straight day on Friday, but it has mainly hit areas held by rival insurgent groups rather than the Islamic State fighters it said it was targeting, drawing an increasingly angry response from the West.
British Prime Minister David Cameron said on Saturday Putin was making the situation worse by helping the "butcher Assad" and urged world leaders to work towards a political transition in Syria.
In an interview with the Sun newspaper, British Defence Secretary Michael Fallon said the vast majority of Russian air strikes were not aimed at the militant group at all.
"Our evidence indicates they are dropping unguided munitions in civilian areas, killing civilians, and they are dropping them against the Free Syrian forces fighting Assad," he said. "He's shoring up Assad and perpetuating the suffering."
Cameron has said he sees a strong case for conducting British air strikes against Islamic State in Syria, but he wants to make sure he has enough support in parliament to gain approval.
Cameron lost a parliamentary vote on the use of force in Syria in 2013. Consequently, British bombing so far has only targeted Islamic State in neighboring Iraq.
"It is absolutely clear that Russia is not discriminating between ISIL (Islamic State) and the legitimate Syrian opposition groups, and as a result they are actually backing the butcher Assad and helping him and really making the situation worse," Cameron told broadcasters.
"We should be using this moment now to try to force forward a comprehensive plan to bring political transition in Syria, because that is the answer for bringing peace to the region."
Defence Secretary Fallon said the British government had made progress in persuading lawmakers from the opposition Labour party to back strikes in Syria and said Putin's involvement would not stop the government from seeking parliamentary backing.
"We can't leave it to French, Australian and American aircraft to keep our own British streets safe," he said.
Reporting by Kate Holton, editing by Larry King