Amnesty accused Syrian forces Wednesday of waging "relentless, indiscriminate" attacks against its people as a Syrian army defector warned the regime would use chemical weapons as a last resort.
The London-based rights group, which accompanied its report with video footage, said "civilians, many of them children, are the main victims of a campaign of relentless and indiscriminate attacks by the Syrian army."
Amnesty said the findings were based on "first-hand field investigations carried out in the first half of September".
During that period, attacks killed "166 civilians, including 48 children and 20 women, and injured hundreds in 26 towns and villages" in the northwestern regions of Idlib and Jabal al-Zawiya and the northern Hama area.
Amnesty said it had new evidence "of a pattern which has emerged in recent weeks in areas where government forces, pushed into retreat by opposition forces, are now indiscriminately bombing and shelling lost territory -- with disastrous consequences for the civilian population."
It comes as the former head of Syria's chemical arsenal told London's Times newspaper that he had been involved in "serious discussion about the use of chemical weapons, including how we would use them and in what areas."
Major-General Adnan Sillu said he defected from the Syrian army three months ago after being party to top-level talks about the use of chemical weapons on both rebel fighters and civilians.
"We discussed this as a last resort -- such as if the regime lost control of an important area such as Aleppo," he said.
Speaking from Turkey, General Sillu told The Times that he was convinced President Bashar al-Assad's regime would eventually use chemical weapons against civilians, adding that the discussion had been "the last straw" which triggered his defection.
His comments come after German press reported Tuesday that the Syrian army had tested a chemical weapons delivery system.
The Syrian Observatory for Human Rights said at least 65 civilians, nine rebels and 12 soldiers were killed on Tuesday, with more than 27,000 fatalities since the uprising erupted in March 2011. The United Nations says more than 20,000 have died.
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The two-month-old battle for the second city Aleppo remains fluid, with both sides claiming gains in a guerrilla war, Observatory director Rami Abdel Rahman said.
Iran proposed a halt to the violence at a meeting in Cairo on Monday of the Syria "contact group" to which it, Egypt, Saudi Arabia and Turkey belong, Tehran's official IRNA news agency said.
Iranian Foreign Minister Ali Akbar Salehi appealed for "a simultaneous halt in clashes and violence by the sides in Syria, (and) insisted on a peaceful solution without foreign intervention and a halt to financial, military and training support for the Syrian opposition," IRNA reported.
He also suggested that observers from the countries could "monitor the process of stopping the violence in Syria," IRNA added.
Last month, the United Nations withdrew its own observers after both sides failed to adhere to an April ceasefire to which they had committed.
Salehi is due Wednesday in Damascus for talks with Syrian Foreign Minister Walid Muallem, a Syrian government source said.
As the killing continues, the head of a UN commission investigating rights abuses in Syria said they had soared dramatically in recent weeks and that the UN Security Council should take "appropriate action" against war criminals.
"Gross violations of human rights have grown in number, in pace and in scale," Paulo Sergio Pinheiro said on Monday, adding that Assad's regime and rebels, to a lesser extent, had committed war crimes.
Turkish media reported that Syrian troops and rebels clashed on Tuesday for control of the Tall al-Abyad border post with Turkey.
A Turkish diplomatic source contacted by AFP confirmed the clashes and said some shelling had hit inside Turkish territory, but did not indicate if there were any victims or damage.
In other developments, UN-Arab League peace envoy Lakhdar Brahimi was welcomed by 1,300 Syrians at the Altinozu refugee camp in Turkey's Hatay province near the Syrian border, amid anti-regime chants.
Brahimi will meet UN Security Council envoys on Monday to discuss his recent talks with Syria's president, diplomats said.