Heavy shelling in Syrian flashpoint Homs

(ROUGH CUT ONLY - NO REPORTER NARRATION)

Thick smoke from explosions covered the skyline in Homs as activists said Syrian government forces were intensifying their assault on opposition strongholds in the city.

Amateur footage posted on the internet, said to be shot on Tuesday (June 12) in Homs, purports to show sustained shelling in the city.

Reuters cannot independently verify the content of this video, which was posted to a social media website.

On Monday (June 11), United Nations monitors said Syrian helicopters fired on rebel strongholds north of Homs and called for "immediate and unfettered access" to conflict zones where they had heard many women and children were trapped.

U.N. efforts to bring peace to Syria - where a 15-month-old uprising against Assad has turned increasingly violent - have largely come to nothing, with both sides blaming the other for breaking the ceasefire.

Soldiers and militias loyal to Assad have killed at least 10,000 people, according to U.N. figures. The Assad government puts its own losses at more than 2,600 dead.