Cairo bus explosion injures five CAIRO - A bomb blast hit a public bus in the Egyptian capital Cairo on Thursday, wounding five people, the interior ministry said, in an attack that raised concerns that a wave of violence blamed on Islamic militants that has targeted security forces and military for months is increasingly turning to hit civilians. The blast came a day after the government declared its top political nemesis, the Muslim Brotherhood, a terrorist organisation, accusing it of being behind the violence. The group has denied the claim, saying the government is trying to scapegoat it. Egypt saw the deadliest bombing yet earlier this week, when a suicide bomber hit a police headquarters in the Nile Delta city of Mansoura on Tuesday, killing 16 people, mainly police. Bombings and shooting have increased since the military ousted President Mohamed Morsi in July and launched a crackdown on his Muslim Brotherhood and other Islamist supporters. Most of the attacks were originally centred in the Sinai Peninsula, where multiple militant groups operate, but they have spread to other parts of the country. Until now, the attacks have focused on police and the military. In Thursday's attack, a homemade bomb planted in a main intersection went off as a public bus passed in the eastern Cairo district of Nasr City, the interior ministry said. Authorities then found at least one more bomb attached to an advertisement billboard apparently intended to hit security forces who responded to the first, state TV reported. The other two explosives were defused. The explosion shattered windows on the bus, and flying glass injured five people, one of them seriously, the ministry said. Abdel-Fatah Osman, ministry spokesman, told state TV said that the bomb was planted near a school complex and intended "to terrorise people and cause chaos." The site is also near student dormitories of the Islamic Al-Azhar University, which have been the scene of near daily protests by Brotherhood students against Egypt's military-backed interim government. The protests have repeatedly turned into clashes with security forces. Islamic militant groups based in Sinai have claimed responsibility for previous bombings and shooting against security forces and the military. The most prominent militant group, Ansar Beit al-Maqdis, announced it carried out Tuesday's suicide bombing in Mansoura to avenge the "shedding of innocent Muslim blood" at the hands of Egypt's "apostate regime" - a reference to the security forces" crackdown on Islamists following the coup. Security experts have warned that young members of the Brotherhood may turn to violence in retaliation for the government's killings of group's supporters, imprisonment of top leaders and declaration of the group as a terrorist organisation. The terrorist label steps up the authorities" crackdown on the Brotherhood. The 85-year-old group rose to power by winning a string of elections after the 2011 ouster of autocrat Hosni Mubarak, but it now has been shattered, with thousands of its members in prison and others largely on the run. Still, it has continued protests demanding Mr Morsi's reinstatement and sharply opposes a new draft constitution that is to be put to a nationwide referendum on January 14-15. The government contends that the Brotherhood is a national security threat, working with militant groups to organise the campaign of violence, though it has provided no evidence. Mr Morsi and other Brotherhood leaders face trial on charges of conspiring with terrorist groups before, during and after Mr Morsi's one-year presidency.