The air was filled with doom at the Democratic Party of Japan's campaign center Sunday evening as the ruling party came to grips with its sobering defeat in the Lower House election.

While the Liberal Democratic Party swept to victory with New Komeito, many key DPJ members lost in single-seat constituencies, including Chief Cabinet Secretary Osamu Fujimura, education minister Makiko Tanaka and former Chief Cabinet Secretary Yoshito Sengoku.

Prime Minister Yoshihiko Noda, who won re-election in his Chiba constituency, said he will step down as DPJ president.

"I bear the biggest responsibility for this serious loss. I will step down as the president of the DPJ," he said at a news conference Sunday night.

"I take this result very seriously. I apologize for not being able to produce results," he said.

During an interview with media outlets Sunday evening, DPJ Secretary General Azuma Koshiishi said the party must accept the people's decision.

"We are in a very tough situation, but that is the judgment handed down by the people and we must take it seriously and start to rebuild the DPJ," he said.

Koshiishi, who oversaw the DPJ's re-election campaign, hinted that he, too, would resign as the party's No. 2 to take responsibility for the drubbing. "I said I would take command of this campaign and I must firmly accept the results," he said.

The lawmakers blamed the loss on their failure to fulfill the many pledges that propelled them to a landslide victory in the 2009 House of Representatives election, as well as deep internal rifts over key issues ranging from the sales tax hike to the Trans-Pacific Partnership agreement.

"We hope to be reborn as a new DPJ that can meet the public's expectations," he said.