* Also wants fund to explain how it assesses climate risk
* Norway fund is world's largest sovereign wealth fund
* Graphic: tmsnrt.rs/2tskfub (Adds detail)
OSLO, June 28 (Reuters) - Norway's $1 trillion sovereign wealth fund, the world's largest, must assess how the planned phase out of oil and gas exploration and production companies from its investments will be conducted, the finance ministry said on Friday.
As part of Norway's efforts to shift its "rainy day" fund away from oil, the country's parliament on June 12 adopted a plan to drop all dedicated oil and gas explorers and producers, as defined by stock market indices provider FTSE Russell, from the fund's benchmark index.
The fund can still invest in oil firms that have refineries and other downstream activities, so-called integrated companies such as Royal Dutch Shell and ExxonMobil.
The finance ministry wants the central bank, which manages the fund, to present a time schedule for the phase out by Sept. 13 to the finance ministry, which will then establish its own plan.
The fund has previously said that any divestments would take place gradually and over time.
Norway has said the decision is to reduce the exposure of the country's wealth to the risk of a permanent drop in oil prices, but environmental campaigners have seized on it as an example of an investor turning away from the oil industry. Also on Friday, the finance ministry requested the central review and describe its efforts related to climate risk in the fund's investments by Dec. 1.
In particular, it wants the bank to describe how it assesses climate risk across the portfolio, whether it is the companies it is invested in, the real estate properties or its bond holdings.
Reporting by Victoria Klesty and Gwladys Fouche; Editing by Elaine Hardcastle