EL KHUSUS, Egypt (Reuters) - Five Egyptians were killed and eight wounded in clashes between Christians and Muslims in a town near Cairo, security sources said on Saturday, in some of the worst sectarian violence in Egypt for months.

Christian-Muslim confrontations have increased in Muslim-majority Egypt since the overthrow of former president Hosni Mubarak in 2011 gave freer rein to hardline Islamists repressed under his rule.

Four Christian Copts and one Muslim were killed when members of both communities started fighting and shooting at each other in El Khusus north of the Egyptian capital, the sources said. State news agency MENA put the death toll at four.

An angry crowd smashed shops belonging to Christians, residents said. A Reuters reporter saw a burned-out Coptic day care center and several damaged shops belonging to Christian traders. An apartment inhabited by Muslims was also burned.

Residents said the violence broke out on Friday when a group of Christian children were drawing on a wall of a Muslim religious institute.

A Reuters reporter saw what looked like a swastika drawn on the wall. Muslim residents said it had offended them because it looked like a cross.

"I saw the kids drawing on the wall after afternoon prayers so I grabbed them and told them to remove what they'd just written," said Mahmoud Mahmoud al-Alfi, a Muslim resident.

Then another man arrived and started beating the children, drawing a large crowd, he said. The situation escalated when someone drew a gun and fired into the air, killing one boy with a stray bullet.

"Suddenly the area was full of weapons," Alfi said, while weeping Muslim women sat nearby in front of a house, showing pictures of a man they said had been killed during the clashes.

The president's office expressed condolences to the victims and vowed to fight any sectarian violence.

"The presidency ... totally rejects any attempt against the unity and cohesiveness of Egyptian society and will decisively confront any attempt to spark sectarian strife among Egyptian people, Muslim and Christian," according to a statement.

Muslim leaders were also quick to condemn the sectarian violence which comes as Egypt struggles with a severe economic crisis and high inflation after two years of political upheaval.

Grand Sheikh Ahmed al-Tayeb, of Egypt's leading Islamic authority Al-Azhar, urged measures to prevent the situation from escalating and to "preserve the national character which characterises the Egyptian people, Muslims and Christians," MENA said.

"The sectarian riots which happened in El Khusus are unacceptable and grave," Saad al-Katatni, the head of the Muslim Brotherhood political party, said on his Facebook website. "There are some who want to set Egypt ablaze and create crises."

President Mohamed Mursi, a Brotherhood leader elected in June, has promised to protect the rights of Copts, who make up about 10 percent of Egypt's 84 million people.

TIGHT SECURITY

On Saturday the situation was calm but tense in the small town where Muslims and Christians live close to each other but in separate streets. Security was tight with police vehicles parked in the main streets.

Police detained 15 people, a security source said.

In a Christian neighbourhood dozens of angry young men gathered at noon on Saturday, chanting "with our blood and soul we sacrifice ourselves for the cross". The crowds left after a priest came and asked them to leave to calm tensions.

"There are people who want to cause sectarian strife between Muslims and Christians," said a Christian man who gave his name as Kameel. "I've been here longer than 30 years and I have never seen any violence or extremism in our area."

Sectarian tensions have often flared into violence, particularly in rural areas where rivalries between clans or families sometimes add to friction. Love affairs between Muslims and Christians have also sparked clashed in the past.

Since Mubarak was ousted by a popular uprising, Christians have complained of several attacks on churches by radical Islamists, incidents that have sharpened longstanding Christian complaints about being sidelined in the workplace and in law.

As an example, they point to rules that make it harder to obtain official permission to build a church than a mosque.

Last month, a court sentenced a Muslim to death for killing two people in a dispute with Christians in a southern town.

In October 2011, 25 people, most of them Coptic demonstrators, were killed in clashes with troops in Cairo.

(additional reporting by Omar Fahmy and Yasmine Saleh; Writing by Ulf Laessing; Editing by Alistair Lyon and Stephen Powell)