HAMA - Syrian troops backed by tanks raided houses in the city of Hama, searching for activists behind five months of protest against President Bashar Al Assad, residents said. The raids took place a day after security forces killed at least four people among crowds of demonstrators pouring out of mosques in Syria after marking the end of Ramadan, the holy month in which Assad intensified a crackdown on protests. Troops swept through several cities in Ramadan, killing scores of people and triggering Western sanctions and Arab criticism, without crushing the unrest in which the United Nations says 2,000 civilians have been killed. The protesters have also failed to unseat Assad, but they have been encouraged by the fall of Libya's Muammar Gaddafi and rising international pressure on Syria, including a planned European Union embargo on the oil industry, which would disrupt vital inflows of foreign currency at Assad's disposal. US President Barack Obama's administration, which has already imposed sanctions on Syria's oil industry and a state-owned bank, froze the US assets of Foreign Minister Walid Al Moualem and two other Syrian officials on Tuesday. Hama has seen some of the biggest protests against 41 years of Assad family rule and was the first city assaulted during Ramadan. Authorities said the army withdrew by mid-August, but residents reported a significant military presence on Wednesday. “Several light tanks and dozens of buses parked at Al Hadid bridge at the eastern entrance of Hama. Hundreds of troops then went on foot into Al Qusour and Hamidiya neighbourhoods. The sound of gunfire is being heard,” Abdelrahman, a local activist, told Reuters by phone. “These neighbourhoods have been among the most active in staging protests,” he added. Another resident said Toyota pick-up trucks mounted with machineguns and buses full of troops also assembled overnight near al-Dahiriya district at the northern entrance of Hama, 205 km (130 miles) north of the capital Damascus. “The people want the execution of the president,” a YouTube video showed dozens of protesters chanting in Hamidiya after night prayers, shortly before the raid on the district. Most foreign media were expelled from Syria after the uprising began in March, making it hard to verify reports. Hama was scene of a 1982 massacre by the military, sent by Assad's father Hafez Al Assad to crush an Islamist uprising. Activists from Syria's Kurdish minority will hold a conference in Sweden on Sept. 3 to unify efforts against Assad, organisers said. Massoud Akko, a Kurdish writer who lives in Norway, criticised major parties representing the Kurds, who number an estimated one million out of Syria's 20 million population. “Kurdish politicians cannot keep issuing timid statements about the need for reform and stopping the repression as our Arab brethren keep getting massacred,” he said.