Syrian authorities have banned the use of the iPhone, further tightening curbs on activists using the device to expose government violence against pro-democracy protesters, the Lebanese website Al Nashara reported Friday.

Syrian activists based in Beirut provided dpa with a copy of a ban they said was issued by the Customs Department of the Syrian Finance Ministry.

"The authorities warn anyone against using the iphone in Syria," read the statement.

Syria has barred most foreign media from the country since the protests began in March.

Opposition activists have been posting on the internet footage of the violent crackdown on protesters.

More than 4,000 people have been killed in Syria since protests started in mid-March, the United Nations said on Thursday.

"It is enough for any tourist or guest visiting Syria to own an iPhone to be a spy suspect," said one Syrian activist speaking on condition of anonymity for fear of retaliation.

"Steve Jobs must be turning in his grave on learning that his iconic device is banned in his home country," he added.

Jobs, who died in October, was the co-founder and chairman of Apple. Abdel-Fattah Jandali, a Syrian, was the biological father of the Jobs.

Syrian government forces shot dead at least six demonstrators demanding foreign intervention to stop a crackdown aimed at protests against President Assad on Friday, activists said.

Four people were killed in the southern province of Daraa and two others in the central province of Homs, Syrian activists based in Lebanon said.

At least 20 people were also arrested in the rebellious provinces of Homs, Daraa and Idlib.

Earlier, the London-based Syrian Observatory for Human Rights said army defectors attacked an air force intelligence center near the border with Turkey, killing at least eight soldiers.

"Around 50 soldiers also defected in the province of Hama,"
activists said.

Protests, which broke out after Friday prayers, were broadcast live on the Doha-based Al Jazeera from Daraa province, where people chanted "the people want the execution of the president."