The U.S. Department of Justice has said that Boston Marathon bombings suspect Dzhokhar Tsarnaev has been charged with using a weapon of mass destruction and could face the death penalty if convicted.
In a statement, the Justice Department said Tsarnaev has also has been charged with one count of malicious destruction of property by means of deadly explosives.
The 19-year-old was indicted on April 22 in a Boston hospital, where he remains in serious condition.
Dzhokhar Tsarnaev and his brother, Tamerlan, both ethnic Chechens, are accused of carrying out the twin bomb attacks a week ago that killed three people and left 173 wounded.
Tamerlan was killed in a shootout with police on April 18.
Dzhokhar was captured following a massive manhunt and hospitalized for injuries including a gunshot wound to his throat.
The White House rejected calls by some Republicans in Congress to declare Tsarnaev an "enemy combatant," a designation that could give interrogators more freedom when questioning him.
"He will not be treated as an enemy combatant," White House spokesman Jay Carney said. "We will prosecute this terrorist through our civilian system of justice. Under U.S. law, United States citizens cannot be tried in military commissions. It is important to remember that since 9/11, we have used the federal court system to convict and incarcerate hundreds of terrorists."
Two U.S. officials said preliminary evidence from the younger man's interrogation suggests the brothers were motivated by religious extremism but were apparently not involved with Islamic terrorist groups.
Boston and other towns and cities across the U.S. state of Massachussets held a minute of silence on April 22 to commemorate the one-week anniversary of the bombings.
WATCH: Police in Massachusetts said thermal imaging helped locate the fugitive Dzhokhar Tsarnaev, who was hiding out in a boat being stored in a Watertown yard:
"The suspect is in critical but stable condition," Boston Police Commissioner Ed Davis said on April 21. "There is a special interrogation team from the Federal Bureau of Investigation standing by to talk to him. That hasn't happened yet. Until it does and until the investigation moves forward, we won't know definitely what other things may come."
Davis also said the two ethnic Chechen brothers had enough weapons that they were probably planning more attacks.
They are thought to have shot and killed
a campus police officer from Massachusetts Institute of Technology, Sean Collier, on April 19.
Authorities found many unexploded homemade bombs at the scene of the brothers' gun battle with police, along with more than 250 rounds of ammunition.
The parents of the two suggested in interviews with RFE/RL that their sons had been "set up" by U.S. authorities.
The father, Anzor Tsarnaev, said he planned to travel to the United States to seek justice for his sons.
"I want real justice. I have a lot of questions to ask the [American] police and secret services. I am a lawyer myself. I want answers to all the questions that I have on criminal issues, on terrorism. I need to know," Anzor Tsarnaev said. "I have questions to ask of the famous American secret services. They keep spinning their image throughout the whole world, they keep promoting themselves. I need to know how they worked, why, where and so on. I need answers to make a clear picture. I also want to hire a lawyer. I need justice, do you understand?"
The young men's mother, Zubeidat Tsarnaeva, told RFE/RL that her oldest son, Tamerlan, was under surveillance. She claimed he had "been monitored" by the FBI for the last five years and protested at a lack of evidence.
A website used by the so-called Caucasus Emirate -- the Islamist resistance movement in Russia's North Caucasus -- published a statement saying it has no connection with the bombing in Boston.
Meanwhile, the governor of Massachusetts, Deval Patrick, confirmed reports that Dzhokhar Tsarnaev returned to "normal student behavior" after the blasts.
"There is evidence of frankly some normal student behavior in those ensuing days which, when you consider the enormity of what he was responsible for, certainly raises a lot of questions in my mind, and, as I say, more to the point, in the minds of law enforcement as well," Patrick said.
A staff member at the Boston community Islamic center connected to the mosque where the two brothers attended prayers said there was no indication either had been radicalized.
Nicholle Mossalam, who heads the office at the Islamic Society of Boston, told RFE/RL on April 22 that elders and staff members have encouraged community members to bring any information they might have about the two men to the authorities.
She said neither was well known in the local Muslim community.
Based on reporting by Reuters, AP, BBC, dpa, and RFE/RL correspondent Tom Balmforth