SEOUL, April 16 (Xinhua) -- South Korea held a nationwide mourning on Monday over the victims of the sunken ferry Sewol in 2014.

The memorial service, led by the government to mark the fourth anniversary of the tragedy, was held at a group incense altar in Ansan, outside of Seoul, local TV footage showed.

About 5,000 people attended the ceremony, including the bereaved families, politicians, Danwon High School students and ordinary citizens.

On April 16, 2014, the Sewol ferry capsized and sank in waters off the southwestern island of Jindo. A paroxysm of grief swept over the entire nation as victims were mostly high school students on a field trip to the southern resort island of Jeju.

Among the 476 passengers on board the ill-fated ship, only 172 were rescued. A whopping 299 have been confirmed dead, with five others still unaccounted for.

Before the memorial service, about 1,000 people marched some 3.3 km to the group incense altar, wearing a badge of yellow ribbon, which symbolizes the teenage victims, and holding placards that read "We'll remember and act," and "We'll not sit idle."

Heads of the ruling Democratic Party as well as the minor opposition parties, including the Justice Party, the Bareun Future Party and the Party for Democracy and Peace, participated in the memorial ceremony, but none of the main conservative opposition Liberty Korea Party members was present.

The previous government under the impeached President Park Geun-hye was criticized for a botched initial response to the maritime tragedy, one of the motives for the nationwide candlelit rallies in 2016 that led to the impeachment of Park.

Prime Minister Lee Nak-yon said at the memorial service that he cannot quell his furor when he thinks again of the ferry's captain, one of the first to be rescued though most of passengers stayed below decks as they were ordered to stay put through a public address (PA) system.

As the vessel tilted over fast, the passengers trapped below the decks were killed with water rushing in. The prime minister wished the deceased rest in peace.

On Sunday, memorial services were held nationwide to mourn over the victims. People laid flowers before their portraits in memorial altars across the country, demanding the government get to the bottom of the tragedy.

Some people also visited the salvaged hull, which was raised in March last year to the surface and moved to a port in Mokpo, about 410 km south of Seoul. The port fence was filled with yellow ribbons people tied to appease the victims' souls.

President Moon issued a message Sunday, saying he promises to get to the bottom of the truth behind the incident. He said he will fully support the investigation by a special investigatory body into the salvaged hull and why it sank.

Moon said his government will make best efforts not to leave any regret for the bereaved families and all people, adding that he will keep on his pledge to make South Korea a safe country and remember the Sewol ferry tragedy.