Activists say Syrian government forces are intensifying their assault on opposition strongholds in the city of Homs.<br/> <br />Thick smoke from the heavy bombardment covers the city's skyline in amateur footage said to be shot on June 12.<br/> <br />Video said to be shot on June 11 in Homs purports to show a Syrian army vehicle explode in a roadside bombing by rebel forces.<br/> <br />Reuters cannot independently verify the content of these videos, which were posted to social media websites.<br/> <br />United Nations monitors said Syrian helicopters fired on rebel strongholds north of Homs on Monday.<br/> <br />U.N. efforts to bring peace to Syria - where a 15-month-old uprising against Syrian President Bashar al-Assad has turned increasingly violent - have largely come to nothing, with both sides blaming the other for breaking the ceasefire.<br/> <br />Sarah Sheffer, Reuters
