Federal prosecutors Thursday announced they will seek the death penalty against 20-year-old Dzhokhar Tsarnaev in the Boston Marathon bombing, accusing him of betraying his adopted country by carrying out a carefully planned terrorist attack without remorse.

U.S. Attorney General Eric Holder's decision to press for Tsarnaev's execution was widely expected. The twin blasts last April killed three people and wounded more than 260, and 17 of the 30 federal charges against Tsarnaev - including using a weapon of mass destruction to kill - carry the possibility of the death penalty.

"The nature of the conduct at issue and the resultant harm compel this decision," Holder said in a statement of just two terse and dispassionate sentences that instantly raised the stakes in one of the most wrenching criminal cases Boston has ever seen.

Tsarnaev has pleaded not guilty. No trial date has been set.

In a notice of intent filed in court, federal prosecutors in Boston listed factors they contend justify a sentence of death against Tsarnaev, who moved to the U.S. from Russia about a decade ago.

"Dzhokhar Tsarnaev received asylum from the United States; obtained citizenship and enjoyed the freedoms of a United States citizen; and then betrayed his allegiance to the United States by killing and maiming people in the United States," read the notice filed by U.S. Attorney Carmen Ortiz.

Prosecutors also cited Tsarnaev's "lack of remorse" and allegations that he killed an MIT police officer as well as an 8-year-old boy, a "particularly vulnerable" victim because of his age. They also said Tsarnaev committed the killings after "substantial planning and premeditation."

In addition, they cited his alleged decision to target the Boston Marathon, "an iconic event that draws large crowds of men, women and children to its final stretch, making it especially susceptible to the act and effects of terrorism."

Tsarnaev's lawyers had no immediate comment.

Prosecutors allege Tsarnaev, then 19, and his 26-year-old brother, ethnic Chechens from Russia, built and planted two pressure-cooker bombs near the finish line of the marathon in April to retaliate against the U.S. for its military action in Muslim countries.

The older brother, Tamerlan Tsarnaev, died in a shootout with police during a getaway attempt days after the bombing. Dzhokhar Tsarnaev was wounded but escaped and was later found hiding in a boat parked in a yard in a Boston suburb.

Authorities said he scrawled inside the boat such things as "The US Government is killing our innocent civilians" and "We Muslims are one body, you hurt one you hurt us all."

Killed in the bombings were: Martin Richard, 8, of Boston; Krystle Campbell, 29, of Medford; and Lu Lingzi, 23, a Boston University graduate student from China. At least 16 others lost limbs. Tsarnaev is also charged in the slaying of the MIT police officer and the carjacking of a motorist during the brothers' getaway attempt.

Campbell's grandmother, Lillian Campbell, said she doesn't think Tsarnaev should live but isn't sure she supports the death penalty, even though she fears he will "end up living like a king" in prison.

"I don't know, because it's not going to bring her back," she said. "I don't even like to discuss it because it makes me so upset. She was my granddaughter and I miss her so much."

Well before the attorney general's decision came down, Tsarnaev's defense team added Judy Clarke, one of the nation's foremost death penalty specialists. The San Diego attorney negotiated plea agreements that saved the lives of such clients as the Unabomber and Olympic Park bomber Eric Rudolph.

Legal experts have said that court filings suggest the defense will try to save Tsarnaev's life by arguing that he fell under the evil influence of his older brother.

In a statement, Massachusetts Gov. Deval Patrick said: "One way or another, based on the evidence, Tsarnaev will die in prison." He did not say whether he supports the decision to seek the death penalty. Patrick opposes capital punishment.

"In each milestone of this case - today's announcement, the trial and every other significant step in the justice process - the people hurt by the marathon bombings and the rest of us so shocked by it will relive that tragedy," he said.

Massachusetts abolished its state death penalty in 1984, and repeated attempts to reinstate it have failed in the Legislature.

The American Civil Liberties Union of Massachusetts, which opposes the death penalty in all cases, objected to Holder's decision.

"After the horrible marathon attack, this community rallied around the slogan `Boston Strong,"' said Carol Rose, executive director of the ACLU. "Even - and especially in a case like this - that means not letting terrorists or anyone else shake us from staying true to our values."

Since the federal death penalty was reinstated in 1988, 70 death sentences have been imposed, but only three people have been executed, including Oklahoma City bomber Timothy McVeigh in 2001.

The last federal execution was in 2003, when Gulf War veteran Louis Jones Jr. was put to death for kidnapping 19-year-old Army Pvt. Tracie McBride from a Texas military base, raping her and beating her to death with a tire iron.