As a joint operation by US and Iraqi troops to take control of Baghdad begins to bear fruit, there were signs on Thursday that their insurgent foes are trying to counter them with deadly new tactics.
Iraqi medics were treating patients poisoned by what is thought to be chlorine gas after attackers targeted civilian areas with trucks rigged as dirty bombs, said Qais Abdulwahab, director of the Kadhimiya Hospital.
But daily bomb attacks on civilians continue, and the use of chlorine and anti-aircraft tactics has underlined what US commanders say is the insurgents' main strength -- their ability to adapt and exploit their foes' weaknesses.
"One of the things we see as we deal with this is that as one technique works in one part of the country we tend to see copycat attacks in other parts of the country," said US spokesman Lieutenant Colonel Chris Garver.
On Tuesday, a truck carrying chlorine gas exploded in Taji, just north of Baghdad, killing six people on the spot but also poisoning scores more as the toxic gas spread through the area, overcoming women and children.
On Wednesday, the dirty bombers struck again, in the suburbs of Baghdad, in a less successful attack that nevertheless spread panic.
"The material used is poisonous," said Abdulwahab. "During the explosion it changes into a mist that spreads through the air, causing poisoning in the breathing system, breathing difficulties and acute coughing.
"It's is the first time we have seen such poisoning cases," he told AFP, comparing the injuries to the internal burns suffered by children who drink chlorine-based cleaning products.
Kadhimiya Hospital treated 90 patients poisoned in Tuesday's attack -- seven of whom died -- and 21 more on Wednesday, Abdulwahab said.
"They've adapted the car bomb tactic," Garver said. "It shows some of the maliciousness with with they are adapting those tactics.
"It was not a chlorine tanker it was just a tank in the back of a truck. The use of canisters with something in them is not new, they've tried using regular acetylene tanks to increase the size of the explosive," he said.
"So that's not new, we do look for canisters already, but obviously we are going to pay more attention now to any kind of canister," he said.
Read More Here: Iraq Insurgents Use Chlorine in Bomb Attacks