Abe held a news conference early in the evening of September 25 to announce he was dissolving the Lower House when it convenes September 28.
Earlier, the head of Mr Abe's junior coalition partner, Natsuo Yamaguchi, said he understood the election would be held on 22 October.
While speaking at a press conference on Monday, Abe said that he is aiming to get support from the people for his hard line against North Korea's nuclear programmes also.
Opposition parties have criticised the vote as a way for Abe's to avoid recent scandals, including allegations of cronyism, which representatives promised to address on Thursday.
A poll published in the Nikkei newspaper on Monday said Abe's LDP received 44 percent of support, compared to 8 percent for both Koike's group and the Democratic Party.
Despite a recent run of growth, the election victor will also have to contend with a sluggish economy, as the heavily indebted country grapples with a low birth rate and a shrinking labour force.
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Tokyo Governor Yuriko Koike on Monday announced the creation of a new party which she will use to jump to politics at the national level.
Ishiba is a probable challenger for Abe next year, along with Fumio Kishida, who left the cabinet for a role as party policy chief last month. If Abe's Liberal Democratic Party maintains its majority in the Diet, he could serve as prime minister until 2021. While highlighting his government's resolve to protect the people's lives and properties, he said, "North Korea's threats should never influence the election, which is the point of origin for democracy".
Abe also revealed that a 2 trillion yen ($18 billion) stimulus package would be prepared by the end of the year.
Ruling Liberal Democratic Party senior official Koichi Hagiuda responded to concerns about the election's timing. The crisis appears to have given him a boost in opinion polls after a series of scandals, and may help him retain his coalition's two-thirds majority in the lower house of Parliament.
As Mr Abe addressed reporters, more than 100 protesters gathered outside the Prime Minister's Office to demand his resignation.
That was higher than the 27.7% a Kyodo news agency survey showed voting for Abe's party, with 42.2% undecided.