Description:Smoke clung to the skyline in Homs and just as it appeared to be clearing, another explosion --- as activists reported government forces were intensifying their assault on the city. Reuters cannot independently verify the content of this video, which was posted to a social media website. The heaviest shelling was directed at a part of Homs inhabited mostly by Sunni tribal families and there are reports that rebel outposts in Rastan and other parts of central Syria are also under heavy fire.(1:36)