Prime Minister Shinzo Abe asked Iranian leaders during his Tehran visit to release Americans detained by the country at the request of U.S. President Donald Trump, a Japanese government source said Friday.

At least four Americans, including a navy veteran who has been sentenced to 10 years in prison, are being detained in Iran.

Abe is believed to have requested the releases during his talks with Iranian President Hassan Rouhani on Wednesday and Supreme Leader Ayatollah Ali Khamenei on Thursday, the source said. It is not known how they responded.