Black smoke billows over the Syrian city of Homs.<br/> <br />Video uploaded to a social media website purportedly shows Homs being bombarded by government forces.<br/> <br />Reuters cannot independently verify the footage.<br/> <br />Authorities are attempting to subdue a year-long uprising.<br/> <br />But residents say the shelling is killing civilians and rebels indiscriminately.<br/> <br />On Monday, Turkey closed its embassy, following the example of many Arab and Western states.<br/> <br />Once a close ally of Syrian leader Bashar al-Assad, it joins a growing number of major powers calling for him to step down.<br/> <br />Jessica Gray, Reuters
