SBI Holdings¡¯ brokerage arm was temporarily banned from some trades related to initial public offerings after Japan¡¯s financial regulator said it manipulated stocks, in the country¡¯s second major trading scandal in recent years.

The Financial Services Agency on Friday instructed the nation¡¯s biggest online broker SBI Securities not to solicit trade orders from clients for shares on the day they list. The curbs are effective through Jan. 18. Officials also required the firm to submit a plan to improve operations by Feb. 13, the regulator said in a statement.

While the ban of less than a week is largely symbolic, it comes at a delicate time for Prime Minister Fumio Kishida¡¯s administration, which is trying harder to persuade Japan¡¯s cash-loving households to invest rather than save in order to help the economy. The country¡¯s stock market has been under scrutiny since local authorities charged SMBC Nikko Securities about two years ago with market rigging.

SBI¡¯s shares closed 2.7% lower Friday, the biggest drop in about a month after an earlier media report of the planned regulatory action.

Securities companies have a key gatekeeper role to play, an official at the regulator said at a briefing in Tokyo. It is problematic for them to do anything that undermines fairness in trading and the acts are likely to impact market confidence, the official said, without being named in accordance with the agency¡¯s policy.

Led by Chief Executive Officer Yoshitaka Kitao, SBI boasts 11 million client accounts for securities trading, more than Nomura Holdings or any other rivals at home. The company has made headlines over recent years by slashing commissions for domestic stock broking to zero, acquiring a midsized Japanese lender and pushing into semiconductor manufacturing.

The probe into the brokerage concerns three stocks that listed in 2020 and 2021 following IPOs underwritten by SBI Securities. Staff at the brokerage asked investors to place buy orders at IPO prices to ensure that they didn¡¯t fall when they started trading, according to the Securities and Exchange Surveillance Commission, the FSA¡¯s investigative arm.

At least three executive officers and one board member of the brokerage unit at the time were involved, according to a statement last month from the watchdog.

The FSA will make SBI clarify who is responsible and take measures if needed, the official said at the briefing.

In an earlier and more serious case, SMBC Nikko Securities was found guilty of market manipulation last year. That led to record losses at the unit of Japan¡¯s second-largest banking group, though its performance has since rebounded.