KANO, Nigeria: The parents of the Nigerian "underwear bomber" who tried to blow up an airliner on Christmas Day 2009 have urged the U.S. to review the life sentences given to their son, said a statement Friday.

A judge in the US state of Michigan on Thursday condemned Al-Qaeda-linked Umar Farouk Abdulmutallab to four consecutive life sentences for his botched attempt to blow up the airliner as it approached Detroit.

"We strongly appeal to the American Justice Department to review the life sentence," Abdulmutallab's family said in the statement sent to the media in Nigeria.

"We also appeal to the Federal Republic of Nigeria to... engage with the American government to ensure that a review is made to show justice in accordance with the circumstances of Umar Farouk's case," the statement continued.

In court, Abdulmutallab declared he was "proud to kill in the name of God" as he defended his botched attempt to kill the 289 people on board Northwest Airlines Flight 253 that originated in Amsterdam.

The family said they learned of the "unfortunate news" of the foiled attack on December 26, 2009.

"It was with tremendous shock that we discovered our son, Umar Farouk, was allegedly involved," the statement said.

"This was so because even though he had gone missing by that time and there were concerns about his situation, he was nevertheless the last person anyone who knew him would link to such actions.

"We are grateful to God that the unfortunate incident of that date did not result in any injury or death. We pray for a more peaceful world," the statement also said.

In October or November of 2009, Alhaji Umaru Mutallab -- the bomber's father -- approached US embassy officials in the Nigerian capital and said he was worried his son had become radicalized by extremists in Yemen.

Mutallab, a British-educated prominent banker who serves on the board of several Nigerian companies, however gave no indication that his son planned an attack.

US authorities therefore did not add Abdulmutallab's name to a "No Fly" list and the failure to act on the father's warning struck a blow to the reputation of the US intelligence services.

Days after the thwarted bombing, the bomber's family offered full cooperation to US authorities. Mutallab was then interrogated by the CIA and FBI in Abuja about his son's actions.

In the statement, the family thanked "the American Government for facilitating visits to check on (Abdulmutallab's) welfare and show love and support."

The would-be suicide bomber showed no remorse during sentencing in the Detroit court on Thursday, saying he was carrying out the work of God against the "oppressors" of Muslims.

Despite stringent security measures at airports in the wake of the September 11, 2001 attacks, Abdulmutallab managed to smuggle more than 76 grams of the explosive Pentaerythritol tetranitrate on board the flight from Amsterdam.

But the bomb hidden in his underwear failed to properly detonate and instead simply caused a fire as the plane began its descent to Detroit.

Passengers and crew members were able to restrain Abdulmutallab and extinguish the blaze, allowing pilots to safely land the plane.