Cairo (CNN) -- Egypt's interim military government Tuesday added two more key figures to its list of Muslim Brotherhood leaders under arrest: Mohamed Badie, the group's spiritual leader, and Safwat Hegazy, a preacher and hardline supporter of the movement.
They were among about 100 members of the Muslim Brotherhood taken into custody Tuesday.
The brotherhood -- locked in a deadly battle with the military for control of Egypt -- slammed the interim government's ongoing "bloody military coup."
In a statement, the group's Freedom and Justice Party described the charges against Badie as "trumped up" and "political."
"It is well-known that all the charges brought against the leaders of the Muslim Brotherhood and its affiliated political party, the Freedom and Justice Party (FJP) as well as the leaders of the Anti-Coup, Pro-Democracy National Alliance are implausible fabricated charges with no legally acceptable evidence.
"What they are facing are nothing but political trumped up charges thinly painted with criminal colors," Ali Kamal, a lawyer for the Muslim Brotherhood, said in the statement.
Badie was taken in a dawn raid at a residential apartment in Cairo's Nasr City neighborhood, the Ministry of Interior said.
Arresting Badie "is not the end of the group, which will remain in the hearts of millions of Egyptians," said Ahmed Arif, spokesman for the Muslim Brotherhood.
Badie will be detained for 15 days for investigation on accusations of inciting violence and killing protesters, the Ministry of Interior said. The detention could be extended, as has been done with ousted President Mohamed Morsy.
Mahmoud Ezzat, Badie's deputy, was named supreme guide on a temporary basis.
Later, Hegazy was arrested in Nasr City as well, according to state-run broadcaster Al-Masriya.
The military has been arresting numerous key figures in the Muslim Brotherhood, including Mohamed Mahdi Akef, the former supreme guide; his deputy, Khairat al-Shater; Saad al-Katatni, chairman of the Freedom and Justice Party; his deputy, Rashad al-Bayoumi; and Sheikh Hazem Salah Abo Ismael.
Armed fighters holed up in school facility, military says
Badie was with Syed Abdul Rahim Abdel Naby, a teacher from the Islamic Dawa school in Beni Suef, when he was arrested at dawn, the Ministry of Interior said in its statement.
Security forces then searched the school and arrested 38 members of the Muslim Brotherhood "who were hiding" in the facility and had numerous weapons, including a rifle, pistols, and Molotov cocktails, the statement said. Some of the equipment belonged to the administration of the civil protection unit in Beni Suef, which had been stormed, robbed and set on fire, the statement said.
Both sides in the conflict have insisted they reject violence, but fighting has raged.
The Muslim Brotherhood changed its profile image on Facebook on Tuesday to an image of Badie, with a quote saying, "Our peaceful movement is mightier than their tanks."
Security forces also arrested 56 administrative leaders of the Muslim Brotherhood in various provinces, the Ministry of Interior said.
The arrests came a day after 25 soldiers were killed in a Sinai ambush and onetime ruler Hosni Mubarak won acquittal on a corruption charge.
The soldiers were killed when suspected militants armed with rocket-propelled grenades struck two buses carrying security forces Monday in the city of Rafah, on the border between Egypt and Gaza, Nile TV reported.
Interim President Adly Mansour declared three days of national mourning following the attack, Nile TV said.
The Sinai Peninsula is a lawless area that was the site of frequent attacks even before Egypt's latest round of turmoil. In May, for example, seven Egyptian solders were kidnapped and held for six days there, a spokesman for Egypt's armed forces said.
But the attack adds to the persistent tension across the country since the military ousted the democratically elected Morsy in a coup.
Over the past week, about 900 people -- security personnel as well as citizens -- have been killed.
Deaths occurred when the military used force to clear two pro-Morsy sit-in sites in Cairo on Wednesday and violence raged after pro-Morsy supporters staged demonstrations Friday.
CNN's Saad Abedin reported from Cairo; CNN's Mohammed Tawfeeq, Ali Younes, Schams Elwazer, Ian Lee, Reza Sayah, Hamdi Alkhshali, Slma Shelbayah, and Holly Yan contributed to this report.