Sparks continue to fly in the increasingly tense battle between Mahmoud Ahmadinejad, Iran's term-limited president, and Ayatollah Ali Khameini, its divinely-appointed supreme leader, the New York Times reports.

Tensions have escalated over the past several years, though they only surfaced publicly in April, when, according to the Times report,

"Mr. Ahmadinejad tried to fire Heydar Moslehi, the intelligence minister, and the supreme leader ordered him reinstated. Mr. Ahmadinejad pouted at home for 11 days, returning only after the supreme leader signaled that the president, too, could be replaced."

Since then, the president has continued to struggle with cabinet appointees. His deputy foreign minister resigned on Tuesday after only three days on the job.

Tensions between the president and the supreme leader are common in Iran, though they are almost always kept from public view.

The Times' Neil MacFarquhar reports that the religious establishment allied with the supreme leader has opened an investigation into alleged vote-buying during the tumultuous 2009 presidential elections.

"The fact that the pro-democracy Green Movement made accusations of widespread fraud in that very election was ignored," MacFarquhar notes.