AMMAN (Reuters) - Syrian forces killed four villagers in the central province of Homs on Tuesday in a crackdown on the most defiant centre of opposition to President Bashar al-Assad in an eight-month-old uprising, activists said. Two children, aged around ten, were among those killed when tanks fired machineguns at villagers in the main street of Tal Dao in the Houla region, 22 km (14 miles) northwest of the Homs, the provincial capital, who had ignored a curfew announced by loudspeakers from tanks, they said. "There was a strike in Tel Dao today and most shops were closed after two people were killed yesterday. But there were still people in the street. This is a rural region and people are not used to curfews," said one of the activists, who gave his name as Abu Raed. Turkish Prime Minister Recep Tayyip Erdogan called on his former ally Syrian leader Bashar al-Assad to step down. "Quit power before more blood is shed ... for the peace of your people, your region and your country," Erdogan said in parliament. After weeks of mounting criticism of the Syrian leader, it was the first time the Turkish premier had directly called for his removal from power. He is the second regional leader to do so, after Jordan's King Abdullah last week called on him to go. "Bashar al-Assad is saying he will fight to the death. Fighting your own people ... is not heroism but cowardliness," Erdogan said, referring to a recent interview with Assad published by the Sunday Times in London. "If you want to see someone who fought and died, take at look at Nazi Germany, take a look at Hitler, take a look at Mussolini and Romania's Ceausescu," he said. If the Syrian leader had failed to learn lessons from history, Erdogan invited him to consider the more recent fate of Libya's late strongman Muammar Gaddafi. The opposition Syrian National Council said Tuesday it is organising a conference with the Arab League to prepare for a "transitional period" after the fall of President Bashar al-Assad's regime. Assad is under mounting pressure from Syria's neighbours to step down over his regime's eight-month crackdown on protests that the United Nations says has killed more than 3,500 people since mid-March. "The Syrian National Council, in cooperation with the Arab League, will organise a national conference to prepare for the transitional period in Syria," it said in a statement received by AFP in Nicosia. The SNC, the largest and most representative Syrian opposition grouping, said it was in talks with activists and dissidents to prepare for the transition "in accordance with the Arab League initiative." "It was determined that the conference will issue a memorandum concerning the post-Syrian regime phase," it said, adding this would ensure "inclusivity and the participation of all political forces in Syria." On Monday, British Foreign Secretary William Hague urged the Syrian opposition to unify to become stronger as he held his first meetings with their representatives in London. France's foreign minister, Alain Juppe, issued a similar call last week, saying "the SNC must get organised" before it can win recognition from the French government. The SNC has so far only been officially recognised by the new post-Gaddafi Libyan authorities.