South Korea laid to rest 46 sailors killed in the sinking of a navy warship during an emotional and solemn burial Thursday, as officials vowed retaliation against those responsible for what many believe was a North Korean attack.

Wailing families placed white chrysanthemums, burned incense and bowed in front of the framed photos of the men before their cremated ashes were buried at the country's national cemetery in the central city of Daejeon. Buddhist and Christian clergy offered prayers and a dirge was played.

Some mothers clad in black Korean traditional mourning dress wailed uncontrollably, touching photos of their sons and their urns wrapped in white cloth.

"It's your mother! Please answer me! Please answer me!" one mother shouted.

The sailors went down with the 1,200-ton Cheonan near the tense western sea border with North Korea on March 26 shortly after it was torn apart by what investigators believe was an underwater blast from outside the ship.

The bodies of 40 of the sailors were recovered, while six others remain unaccounted for and are presumed dead. Belongings of the missing were burned and the ashes were among those buried Thursday.

South Korea has not directly blamed its Cold War-era rival North Korea, but suspicion has focused on Pyongyang given its history of provocations and attacks on the South. South Korea's defense minister said this week the blast was most likely caused by a torpedo attack. North Korea has denied any role.

Earlier Thursday, sirens blared across South Korea when the funeral started at the 2nd Fleet headquarters in Pyeongtaek, south of Seoul, the ship's home base. Warships anchored there sounded whistles, and seamen aboard saluted when the vehicles carrying the ashes left for the cemetery.

A somber President Lee Myung-bak and his wife _ who joined 2,800 mourners at the ceremony _ paid homage to the sailors, while buglers played taps. Former President Chun Doo-hwan, lawmakers and military leaders also paid respects to those who died in one of South Korea's worst naval disasters.

The name of each sailor was read out while Lee, clad in a black suit and tie, placed military decorations on a giant alter below photos of each man. They had all been posthumously promoted by one rank in recent days.

"The Cheonan is engraved as history into the people's hearts and your honorable sacrifice is being reborn as patriotism," Chief Petty Officer Kim Hyun-rae, one of the 58 survivors of the disaster, said in an address to the funeral.

Tears welled up in the eyes of President Lee as he listened to Kim's speech.

About 3,000 white and black balloons were released into the air.

The Cheonan was on a routine patrol before it split in two and sank near the disputed western sea border, a scene of three bloody sea battles between the rival Koreas that remain locked in a state of war since their 1950-53 conflict ended in a truce instead of a peace treaty.

"We cannot forgive this and must not forgive it and must not forget it," Navy Chief of Staff Kim Sung-chan said in a speech at the funeral. "We will never sit idly by in the face of whoever inflicted huge pain to our people. "

Military retaliation against Pyongyang, however, is considered unlikely as it could lead to major conflict and frighten away investors at a time when South Korea is recovering fast from the global financial meltdown and prepares to hold a summit of leaders from the Group of 20 in November.

North Korea has waged a slew of attacks against South Korea, including a 1987 downing of a South Korean passenger plane that killed all 115 people on board, one of the reasons the country is suspected of involvement.

In central Seoul people gathered Thursday at a plaza to remember the Cheonan sailors, placing chrysanthemums on an altar where photos of the dead were placed.

"I feel empty," said mourner Lee Yoon-suk, tears were rolling down her cheeks "I truly hope they rest in peace in heaven."

Mourners also wrote condolence messages.

"Thank you for keeping us safe," read a message left by a Kim Yeon-Joong. "You are now forever discharged from duty. Rest in peace. This is Korea's final order to you."

One of the pictures drew special interest as rainwater that fell Tuesday and Wednesday dripped over it. On-lookers paid their respects by wiping the water from Kang's face, telling him not to cry.

Flags in South Korea are flying at half-staff and many government buildings in Seoul have hung large black-and-white placards reading, "We will not forget your honorable sacrifice."

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Hyung-jin Kim reported from Seoul, South Korea. Associated Press writers Sangwon Yoon, Nate Kim and Kelly Olsen in Seoul and AP Television News cameraman Yong-ho Kim in Pyeongtaek, South Korea contributed to this report.