Two universities in Osaka Prefecture evacuated their campuses on Monday after a bomb threat was made criticizing the English name of their planned new merged school, the operator of the schools said.

A bomb threat against Osaka Prefecture University and Osaka City University was sent by email to the Sakai city office, saying it was "retribution against the English name" of the new university, according to University Public Corporation Osaka, which operates the schools. Osaka Prefecture University is located in Sakai.

The email said the bombs will detonate at noon on Wednesday and sarin gas will be released on their campuses.

Last Friday, the operator said the two universities will merge in fiscal 2022 and the new school will be named the University of Osaka.

However, the decision came under criticism from Osaka University, a national university in the same prefecture, saying the new name is "confusing."

"The name is incredibly similar to our university, which is already well-established abroad, and can become a hindrance to both schools' futures," Osaka University President Shojiro Nishio said in a statement following the announcement last week.

He added that "University of Osaka" was already recognized abroad as Osaka University, and could be confusing for overseas universities, as well as when citing for research papers.

Osaka University asked the operator, the prefecture and the city of Osaka to reconsider the name but Osaka Gov. Hirofumi Yoshimura said the new name will not cause confusion and they would not consider changing it.

According to an online poll of foreign students at Osaka University, nearly all said the new name would cause confusion and some voiced concerns over any potential impact on their future employment and study in other countries.

"Many of us at the school are quite angry about this," an Osaka University official said.

An Osaka prefectural government source said possible confusion in research papers had been discussed but it had not led to reviewing the name, given similar cases such as Nagasaki University, a national university in Nagasaki Prefecture, and the University of Nagasaki established by the prefecture.

Osaka Mayor Ichiro Matsui has said he will aim to hold a referendum later this year on whether to restructure the western Japan city into a metropolis like Tokyo to achieve more effective governance.

Depending on the fate of the plan, "the new name might be 'Osaka Metropolitan University,'" a senior official of the Osaka prefectural government said.