A council of port cities in Japan has asked the U.S. military via the Foreign Ministry to make sure it notifies the Japanese before any U.S. nuclear-powered vessels make port calls in the country, Kyodo News reported Friday.

The move came after an unannounced port call by the USS Providence, a nuclear-powered submarine, in Okinawa Prefecture on Monday drew protests from the national and local governments.

Under a bilateral agreement, the United States is supposed to notify local municipalities through the ministry of any port calls by such vessels at least 24 hours in advance.

Monday’s port call by the Los Angeles-class attack submarine occurred at White Beach in Uruma, Okinawa. It was the first such call by a U.S. nuclear sub since Japan and the United States confirmed the notification rule in writing seven years ago.

The U.S. blamed the situation on a communication error within the Navy, according to the Kyodo News report.

The new council, headed by Yokosuka mayor Ryoichi Kabaya, told the news service it is requesting that U.S. forces not repeat the event so local residents can feel more at ease about their safety.

"The importance of this prior notification system has grown, partially because of the revelation of radioactive leakage from a U.S. nuclear submarine," Sasebo mayor Norio Tomonaga said at a Yokosuka news conference, according to the report. "I want [U.S. forces] to adhere to the rules."

Concerns among Japanese remain high after it was discovered the USS Houston seeped small amounts of radioactive water during visits to Sasebo in March and April. Secretary of the Navy Donald Winter called the amounts "undetectable by any mechanism" while visiting Sasebo Naval Base in September.

The sub also leaked in Yokosuka, Okinawa and Guam.

Kyodo News reported the committee is made up of officials from Yokosuka, Maizuru in Kyoto Prefecture, Kure in Hiroshima Prefecture and Sasebo.

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