Fifteen Iranian individuals and 13 institutions designated by a UN resolution as being involved with Iran's nuclear programme will be added to a list of those whose assets have already been frozen, the government said.
The UN Security Council has imposed two rounds of sanctions on Iran since December, but Tehran has refused to halt work on enriching uranium, saying the process is used to fuel power plants to produce electricity.
Iran has installed 1,600 centrifuges used for enriching uranium and is set to introduce more as part of its nuclear programme, according to a senior Iranian official quoted by Iran's Mehr News Agency.
''We need to take strong measures given the need to maintain a non-proliferation framework, its ties to the North Korean nuclear issue and its impact on the stability of the Middle East,'' Chief Cabinet Secretary Yasuhisa Shiozaki told a news conference.
Japan will also freeze fresh grant aid or yen loans to Iran, except for humanitarian and development purposes, Shiozaki added.
Resource-poor Japan has found itself in a bind between the need to meet its energy requirements and its desire to stay in line with Washington, its closest security ally.
But officials have said they would not allow Tehran to possess nuclear weapons nor compromise that position because of Iran's rich oil resources.