This is what appeared on the official FIDE web site (click to enlarge):
The text reads: "At the end of the Board meeting held in Athens, Greece on the 26th March 2017, Mr Kirsan Ilyumzhinov announced his resignation from the position of FIDE President. The Presidential Board has been formally advised of this announcement and an extraordinary board meeting has been called in April."
On the web site of the Russian Chess Federation we see the following:
The accompanying text reads: "Kirsan Ilyumzhinov, speaking on a phone with RCF PR-director Kirill Zangalis, clarified the issue with his alleged resignation from FIDE.
My resignation was never discussed officially during the FIDE Presidential Board. It all started when the US Government included me into the sanctions list”, - told Kirsan Ilyumzhinov. - “After that my ill-wishers began hoping to remove me from the position of the FIDE President. During the Presidential Board in Athens, such suggestion was emanated from the US Chess Federation. However, I want to stress that this topic has never been on the agenda – such talks only took place on the sidelines. Perhaps people who wanted to replace me mistook their wish for the reality. I continue to work in the ordinary course.”
On the news page of Radio Free Europe we find a more detailed explanation:
Ilyumzhinov immediately hit back at FIDE's announcement of his resignation, telling the state-run TASS news agency the same day that he had "not signed anything, and I don't plan to step down." Later, he told Russian state television that "[FIDE presidential] elections are due in September ; thus there are 1½ years to go, and then we'll see." "At the moment I am carrying out my duties as FIDE president," he said.
Ilyumzhinov, who was hit with U.S. sanctions in 2015 over his alleged support of Syrian President Bashar al-Assad, added that he saw "American hands" in what he called a plot to oust him at FIDE. "These are intrigues of the American chess federations and their allies," he was quoted by TASS as saying. "They've repeatedly tried to do this. In Athens, they tried to raise the issue of my resignation, but it didn't work. In general, I am even getting threats. They’re demanding that I resign."
There's a lot more to read on the Radio Free Euope page.
Andrei Kartashov reports similarly in TASS: Kirsan Ilyumzhinov, President of the International Chess Federation (FIDE), told TASS on Monday that he never submitted any resignation despite earlier media reports. "They wanted to oust me, but they could not pull it off," Ilyumzhinov said in an interview with TASS. "I did not sign anything and I am not stepping down."
The full article is here. TASS also points to this article about the blacklisting of Ilumzhinov by the US Department of Treasury, which stated that stating that the FIDE president materially assisted and acted for, or on behalf of the Syrian government.
On he AGOM site Dylan Loen McClain writes: "In a development that could have far-reaching consequences for the World Chess Federation, the game’s governing body, FIDE, as the federation is also known, has announced that Kirsan Ilyumzhinov, its long-time president has resigned. The announcement was made today on the federation’s Web site and was confirmed by Nigel Freeman, FIDE’s executive director.
What happens next is unclear. The FIDE announcement of the resignation said that “an extraordinary board meeting” had been called for April, presumably to name a replacement. But if Ilyumzhinov has not resigned, this may be more like a coup d’etat, in which case there may be legal action ahead.
On the BBC there is a short interview with Malcolm Pein on the Ilyumzhinov power struggle.
Finally you may want to read this extensive article on the subject in The Telegraph.
On Tuesday the above letter (on FIDE letterhead) surfaced.