The Persian-language website gooya.com says Reza Valizadeh was the object of a complaint from the president's office. He was detained on November 26, but his whereabouts are unknown. Iran's judiciary has neither confirmed nor denied Valizadeh's arrest.
Valizadeh wrote on his blog that Ahmadinejad's security staff purchased four dogs in Germany for 150 million toumans each (about $150,000).
He reported that the canines were deployed to sniff out possible explosives on November 14, before Ahmadinejad's appearance at an annual press exhibition. The sweep left exhibition visitors standing outside the venue for several hours.
He also said the price of the dogs and their appearance in public evoked surprise and criticism. Some strict Shi'ite interpretations of the Koran regard dogs as unclean, and dog ownership is controversial in Shi'a-dominated Iran.
The populist Ahmadinejad came to power on promises of returning wealth to the average Iranian, and he carefully cultivates an image of modesty by dressing simply and repeating publicly that he carries a packed lunch to work.
The British daily "The Guardian" reported on November 20 that the use of dogs in the protection of an Iranian head of state could be unprecedented in the 28-year history of Iran's Islamic republic.
Valizadeh quoted an unnamed official as saying the decision to deploy the bomb-sniffing dogs was made by the security team, and was outside the authority of the president.
Crackdown On Critics
Valizadeh's arrest comes two days after dozens of Iranian journalists and intellectuals issued a statement to protest the jailing of journalists who are critical of the Iranian government.
One of the signatories, journalist Issa Saharkhiz, told Radio Farda on November 26 that a government crackdown on journalists has intensified in recent months. "There are some who are sitting and thinking of ways to fill up Iran's prisons. Unfortunately, we now see this not only in Tehran but also in the provinces," Saharkhiz said.
Saharkhiz added that journalists and media workers have lost their jobs as a result, and society has been limited to a "single voice."
In recent weeks, several journalists have been detained or charged in cities like Ahvaz, Rasht, and Sanandaj.
Iran was ranked 166th of 169 countries in Paris-based Reporters Without Borders' index of world press freedoms, published last month.
Iranian officials, including Ahmadinejad, insist there is freedom of speech in Iran. But journalists are frequently charged with security-related crimes.
Rights groups say the atmosphere for free speech has deteriorated since Ahmadinejad came to power in 2005.
(Radio Farda's Ruzbeh Bolhari contributed to this report.)