Syria's deputy oil minister has announced his resignation, saying he is joining the anti-government revolt.
Abdo Hussameddin announced his defection（背叛，缺点） in a video posted on YouTube.
He is the highest ranking civilian to abandon President Bashar al-Assad since the uprising erupted a year ago.
His announcement comes after the UN humanitarian chief said parts of Homs had been "devastated", following a visit to the city bombed by Syria's government troops.
Valerie Amos said the bombed-out Baba Amr district felt like it had been closed down entirely.
The government retook the district last week after fierce shelling.
Activists say troops committed massacres（大屠杀，惨败） since they entered. Damascus blames rebels for many deaths.
Opposition groups said 39 people were killed across the country on Wednesday, of whom 26 were in Homs, six in Idlib, three in Deraa and two each in suburbs of Damascus and Aleppo.
The UN says more than 7,500 people have died as a result of the violence in Syria over the past 12 months.
International media organisations are heavily restricted in Syria, making it impossible to verify the claims of either side.
Mr Hussameddin, 58, posted his video on YouTube late on Wednesday.
"I, Abdo Hussameddin, deputy oil and mineral wealth minister in Syria, announce my defection from the regime, resignation from my position and withdrawal from the Baath Party.
"I am joining the revolution of the people who reject injustice and the brutal campaign of the regime."
Mr Hussameddin - who has been deputy minister since August 2009 - added: "I tell the regime, which claims to own the country, you have nothing but the footprint of the tank driven by your barbarism（野蛮，原始） to kill innocent people."
An activist who shot the video and posted it on YouTube told the AFP news agency in Beirut that the opposition helped to arrange the resignation.
The Syrian government has not publicly commented on Mr Hussameddin's announcement.
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