Reports coming out of Homs, which has been pounded for weeks now by Bashar al-Assad's military, indicate one of the worst days of shelling against a Syrian city since the war started there.

The Syria Observatory for Human Rights says that at least 16 civilians were killed in Homs' Baba Amr neighborhood, three of them children. The BBC reports at least 30 dead in Homs, which has emerged as a stronghold for both armed and peaceful resistance to Mr. Assad's continued rule. Among the dead in Baba Amr was Rami al-Sayyed, a young Syrian who'd devoted himself since July to filming fighting and protest marches. As Syriapioneer on Youtube, he uploaded 831 videos between then and earlier today.

The next to last video on the account posted early today, too graphic to share here, was of Mr. Sayyed sitting beside a man in tracksuit who'd been mutilated beyond recognition. Sayyed was cut down by an infantrymen a few hours later, and the final video on the account is of his body being prepared for burial, uploaded by his brother.

From Peter Bouckaert, a senior researcher for Human Rights Watch, comes an indication why the death toll has been steadily climbing in Homs. He says a video from Homs that shows the fragments of a mortar the struck a building there is proof that Assad has deployed the Russian-made "Tulip" weapons system against the town, which fires the largest mortar round in any military's arsenal. The tank-like vehicle that serves as the firing platform can lob 240mm mortar rounds up to 20 kilometers away, and they carry over 70 pounds of explosives. The largest mortar used by the US, in contrast, is 160mm.

Syria has another Russian-made system for firing rounds that size, the towed M240, and it's possible that's being used to fire the rounds instead of the Tulip.

The Tulip was designed for use against dug in positions from a standoff distance. But its lethality has been used in the past to bring devastation to civilian neighborhoods, most famously by the Russians during the siege of the Chechen capital of Grozny over a decade ago, where thousands of civilians were killed and hundreds of buildings reduced to rubble. The use of such weapons in dense urban environments is a war crime.

There are ongoing international efforts to convince Assad to stand down. But the increasing lethality of the weapons used by his army, and the mounting civilian death toll, paint the picture of a man who has determined to win this fight whatever the cost in lives.

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The first video below is of the 240mm fragments that hit Homs, and the second is a Russian video showing how the weapons system works.

Updated after posting to include information on the M240.