Egypt's military rulers have detained 190 people in connection with the clashes between Muslims and Christians in Cairo in which at least 12 people were killed and more than 230 wounded.
The Supreme Council of the Armed Forces ordered "the transfer of all those arrested in connection with (Saturday's) events, and they number 190, to the Supreme Military Court, as a deterrent to all those who think of toying with the potential of this nation."
The council, which has ruled Egypt since a popular uprising toppled president Hosni Mubarak, also said it would "set up a committee to assess the damage from the clashes" and restore property.
In a statement on Sunday, it also called on "all communities in Egypt, the youth of the revolution, the national forces and Islamic and Christian scholars to stand like a wall against any attempt by the forces of evil and darkness to tear the national fabric."
Egypt's cabinet also said on Sunday in an emergency meeting that it will use an "iron hand" to protect national security.
The government has said it will step up security at religious sites and activate laws dealing with terrorism, to give police more power to prevent interfaith clashes. The rules also enable stricter punishments for vandalizing houses of worship.
Egypt's prime minister had called Sunday's meeting to discuss the sectarian violence, a day after witnesses said a mob of conservative Muslims marched on a Coptic church in the northwestern neighborhood of Imbaba.
The march began over an apparent relationship between a Coptic Christian woman and a Muslim man, amid reports that the woman was being held inside against her will and prevented from converting to Islam.
The verbal clash on Saturday soon developed into a full-fledged confrontation where the two sides exchanged gunfire, firebombs and stones, and another church nearby was set on fire.
Interfaith relationships often cause tension in Egypt, where Christians make up about 10 per cent of its 80 million people.
Al Jazeera's Rawya Rageh said the Cairo neighborhood where the clashes first began remained tense on Sunday, as gunfire rang out briefly outside a church.
"We understand several Christians are huddled inside churches to protect their churches," she said.
"It's very intense, the military is blocking the entire area. Residents have asked us to leave, the military has asked us to leave."
"We understand the military was firing shots into the air to disperse who they are describing as hardline Muslim groups who are at the scene to take revenge for the Muslims who lost their lives in the confrontation last night. At least six of the people who died are believed to be Muslims."
Meanwhile, several thousand Copts have gathered in front of Egyptian state television, demanding the resignation of the country's military ruler.
Al Jazeera's Jamal Elshayyal said that some have been yelling anti-Muslim sentiment.
The strife represents another challenge to Egypt's military rulers who are trying to restore law and order after following the 18-day long popular uprising earlier this year.
The grand mufti of Egypt, Ali Gomaa, a senior Islamic religious figure, called for calm following the clashes. "All Egyptians must stand shoulder to shoulder and prevent strife," he told the state MENA news agency.
He also urged the military council to stop anyone from meddling with the security of Egypt.
Our correspondent said the latest clashes have raised questions over the capability of the country's military leaders to deal with the sectarian crisis.
"The question is being asked ... 'Why is the country's new military leadership not doing enough to deter these attacks that have been repeating since the revolution?' And 'why is the military not doing enough to address the root causes of this tension?'"
Christians in Egypt complain about unfair treatment, including rules they say make it easier to build a mosque than a church.
Claims that Christian women who converted to Islam were kidnapped and held in churches or monasteries have soured relations between the two communities for months.
The religious feuds are a severe blow to the unity Egyptians professed during their popular uprising, when Christians and Muslims often protected each other during prayer.
In the months after the toppling of Hosni Mubarak on February 11, there has been a sharp rise in sectarian tensions, fueled in part by a newly active ultraconservative Muslim movement, known as the Salafis.
On Friday, a few hundred Salafis marched through Cairo celebrating al-Qaeda leader Osama bin Laden and condemning the US operation that killed him.