Hundreds of protesters rallied in London outside Downing Street on Tuesday (September 3) to pressure Prime Minister David Cameron into raising the issue of gay rights in Russia at the G20 meeting in St Petersburg later this week.

Similar protests have been held in 33 cities around the world as part of a global campaign against Russia's anti-gay laws,

Clutching banners bearing slogans such as "Love Russia. Hate Homophobia" and rainbow flags, protesters called for a change in the policy that has attracted criticism from world leaders including U.S. President Barack Obama.

Critics of the anti-propaganda law have said it effectively disallows all gay rights rallies and could be used to prosecute anyone voicing support for homosexuals.

Veteran gay rights campaigner Peter Tatchell attended the protest after holding a meeting with a British Foreign Office minister.

"I've just come from a meeting with the Foreign Office minister Alistair Burt, he's given me his assurance that the Prime Minister David Cameron will raise the issue of gay human rights abuses in Russia with President Putin, when they meet at the G20 summit later this week. That's great news, but I put it to the minister that we'd also like David Cameron to get gay rights put on the G20 summit agenda and for a joint communication by world leaders at the G20 calling for the respect for not only gay rights in Russia but respect for all human rights in Russia," Tatchell told Reuters Television.

U.S. President Barack Obama invited Russian human rights activists to meet him later this week, their groups said on Tuesday (September 3), a few weeks after snubbing Russian President Vladimir Putin amid spiralling disputes over human rights and security.

Presented by Adam Justice