"It is a matter of deep concern that tensions will escalate in the region of the Middle East", Japan's Deputy Chief Cabinet Secretary Yasutoshi Nishimura told a briefing, as cited by Kyodo news agency.
On Monday, acting US Secretary of Defense Patrick Shanahan announced sending of more US soldiers to the Middle East. Shanahan added that the United States was not seeking a conflict with Iran and the additional forces were being sent to protect US interests and personnel in the region.
On Thursday, two oil tankers, Kokuka Courageous and Front Altair, suffered explosions and fires in the Gulf of Oman near the Strait of Hormuz.
While the causes of the incident remain unknown, the United States claimed that Iran had attacked the vessels. However, Washington had not provided any evidence to support its claims.
Iran has denied all the allegations of having a role in the incident.
Russian Deputy Foreign Minister Sergey Ryabkov warned against attempts to lay the blame on Iran before any thorough investigation into the incident.