Egyptian security forces are on high alert, with thousands of people expected to join anti-government rallies after Friday prayers. The government says it is open to dialogue but also warned of decisive measures as the fourth day of violent protests loomed. Widespread disruption has been reported to the internet and mobile phone messaging services. There are also reports of arrests of opposition figures overnight.The reported crackdown on the largest opposition movement, the Muslim Brotherhood, came after it said it would back the Friday protests.On Thursday, Egyptian opposition figure and Nobel laureate Mohamed El Baradei returned to Cairo, promising to join the street protests.At least seven people have died since the protests began on Tuesday. They follow the so-called Jasmine Revolution in Tunisia, which saw President Zine al-Abidine Ben Ali flee into exile.Friday's rallies in Egypt are expected to be the biggest so far, with people being urged via internet sites to join the protests after attending prayers.This is going to be a test for the demonstrators – and the authorities. Arabs across the region are looking closely at what is happening in Egypt as are big foreign powers and Israel. Egypt is the traditional leader of the Arab west Asia- and despite an unpopular peace with Israel, is still highly influential.