The fallen city of Homs, which saw rebels flee after president Bashar al-Assad's forces overwhelmed them with brute force and battlefield-grade firepower, is now the source of "grisly reports," in the strong words of  U.N. Secretary-General Ban Ki-moon. According to the Reuters report, Ban said that soliders were "arbitrarily executing, imprisoning and torturing" anyone left behind.

The claims are corroborated by British photojournalist Paul Conroy, who was injured by a rocket attack earlier this week but escaped from Homs with his life. (Fellow reporter Marie Colvin was not so lucky: She was killed in the same attack.)

From his hospital bed, the Sunday Times photographer told Sky News

"I've worked in many war zones - I've never seen or been in shelling like this ... I'm an ex-artillery gunner so I can kind of follow the patterns - they are systematically moving through neighborhoods with munitions that are used for battlefields.

"It's not a war, it's a massacre, an indiscriminate massacre of men, woman and children."

Watch Conroy's interview here: