DAMASCUS - Regime forces fired on protesters who took to the streets of Aleppo on Friday, wounding several people at the biggest rally seen in Syria's second city since a revolt erupted last year, a watchdog said.The Syrian Observatory for Human Rights said demonstrators also suffered gunshot wounds in Douma, a key protest hub near Damascus, but did not provide any casualty figures. "Thousands of people demonstrated in various districts (of Aleppo) despite the repression," said Rami Abdel Rahman of the Syrian Observatory for Human Rights said. "These are the most important events in Aleppo since the beginning of the revolt," he told AFP in Beirut.The government said its forces foiled a suicide bomb attack in Aleppo last Friday, a day after twin bombings in Damascus killed 55 people and wounded nearly 400. It has repeatedly blamed such attacks on "terrorists".UN chief Ban Ki-moon said on Thursday he believes Al-Qaeda committed the Damascus attack. "Very alarmingly and surprisingly, a few days ago, there was a huge serious massive terrorist attack. I believe that there must be Al-Qaeda behind it. This has created again very serious problems," Ban said.Syrian President Bashar al-Assad, as well as the United States and Russia, has already pointed to an Al-Qaeda presence in the country since the revolt against his regime began. The Observatory said at least seven died in violence across the country on Friday, including two children and a woman killed by regime forces.Besides Aleppo, protests demanding the ouster of Assad also took place in Damascus, the eastern city of Deir Ezzor, northeastern Hasaka, Homs in central Syria, and northwestern Idlib, said the Britain-based Observatory.The Observatory said tens of thousands of people rallies across the country, in the biggest demonstrations since an April 12 ceasefire which has been violated on a daily basis.Meanwhile, Turkish Prime Minister Recep Tayyip Erdogan urged the United Nations on Friday to boost the number of military observers in Syria to far more than a planned total of 300. "Three hundred observers will not be enough ... maybe 1,000, 2,000 or even 3,000 observers are required in Syria," Erdogan told journalists on a visit here. "Syria's entire territory has to be covered with observer missions for everybody to know what is going on, when and where," he added. after talks near Varna with his Bulgarian counterpart Boyko Borisov and visiting Qatari Prime Minister Sheikh Hamad bin Jassem al-Thani."Our biggest concern is that, unfortunately, the plan of (UN-Arab League special envoy for Syria Kofi) Annan is not yet active, it is not being implemented," he added, noting that he and his interlocutors had "overlapping" views on the subject.