Iran's Bushehr nuclear plant begins operation
Iran's first nuclear power station has begun operating at a low level, says the Russian company that built it.
The generating unit at the Bushehr reactor was brought up to the "minimum controllable level of power" on Sunday.
"This is one of the final stages in the physical launch of the reactor," said Vladislav Bochkov, a spokesman for the Russian company Atomstroyexport.
Israel and other nations have expressed fears that the reactor could help Iran develop nuclear weapons.
In February, the International Atomic Energy Agency (IAEA) said it had new information on "possible military dimensions" to Iran's nuclear plans.
But Tehran says its intentions are purely peaceful.
On Monday, a member of an Iranian parliamentary commission monitoring Bushehr said "final tests" were being conducted.
The following day, Atomstroyexport said it had launched "a self-supporting chain reaction" in the "active zone" of the plant's first reactor.
"This means that a nuclear reaction has begun," it said.
Iran's Fars news agency said the plant would start providing power to the national grid within two months.
The Bushehr project was begun in 1970s but it has been dogged by delays.
Construction on the plant was abandoned after Iran's 1979 Islamic revolution until the mid-1990s, when Moscow reached a billion-dollar deal with Tehran to complete it.
In February, Iran had to remove fuel from the reactor "for technical reasons", amid speculation that the Stuxnet computer virus may be responsible.
The United States and other Western nations for years urged Russia to abandon the project, warning it could help Iran build atomic weapons.
But an agreement obliging Tehran to repatriate spent nuclear fuel to Russia eased those concerns.
In February, an IAEA report obtained by the BBC and made available online by the Institute for Science and International Security (Isis) - said Iran was "not implementing a number of its obligations."
These include "clarification of the remaining outstanding issues which give rise to concerns about possible military dimensions to its nuclear programme".
Six world powers are negotiating with Iran over its nuclear programme, and the country is subject to United Nations Security Council sanctions over its refusal to halt uranium enrichment.
Enriched uranium can be used for civilian nuclear purposes, but also to build atomic bombs.