TOKYO (Kyodo) -- Opposition parties wasted no time criticizing Shigeru Ishiba as he was formally picked as Japan's prime minister Tuesday, accusing him of limiting their ability to scrutinize the new government by already suggesting he will soon call for a general election.

"I am deeply disappointed," main opposition Constitutional Democratic Party of Japan leader Yoshihiko Noda told reporters, noting that he had thought Ishiba, who doubles as head of the ruling Liberal Democratic Party, "the type of politician who faces up to debate."

Speaking to Ishiba at the parliament, Noda suggested that the just-convened extraordinary Diet session does not have to end in nine days as the prime minister rushes toward seeking a public mandate.

"The parliamentary session can be extended. Let's have a good debate," he said.

Nobuyuki Baba, leader of the second-largest opposition Japan Innovation Party, said the Ishiba Cabinet is "running away from its enemies" and slammed Ishiba, saying he leaves a "stain" in political history for his rare move of declaring the date of a House of Representatives election even before becoming prime minister.

Ishiba, who won the LDP presidential race on Friday, said Monday that a general election will be held on Oct. 27 to seek a public mandate as his party looks to rebound from a political fundraising scandal, which led to his predecessor Fumio Kishida stepping down.

The next general election must be held by October 2025, when the current four-year terms for lower house members expire. But Ishiba is apparently seeking to take advantage of an expected boost in public support following the leadership change to ensure a majority for the LDP and its junior coalition ally Komeito party.

Ishiba is expected to dissolve the lower house on Oct. 9, the quickest an incoming Japanese prime minister has ever done under the current Constitution. Kishida held the previous record when he dissolved the lower chamber 10 days after becoming prime minister.

Ishiba, a veteran politician who held the defense portfolio in the past, is set to give a policy speech and face questioning from party representatives during the ongoing extraordinary Diet session.

The Japanese Communist Party expressed wariness over Ishiba's proposal to create an "Asian version of NATO" to strengthen regional security, a plan that has drawn criticism from China.

"This is a Cabinet prominently militaristic," the opposition party's chairwoman, Tomoko Tamura, said, vowing a "head-on fight" in the upcoming election.