(Adds suicide attack on tribal leaders, paragraphs 8-10)

By Missy Ryan

BAGHDAD, Nov 9 (Reuters) - The U.S. military on Friday freed nine Iranians held in Iraq, including two it had accused of links to Iran's elite Qods Force, signalling a possible easing of tension between the two foes over security in Iraq.

While U.S. President George W. Bush is still pushing for tougher sanctions against Iran over its nuclear programme, U.S. officials in Baghdad have softened their rhetoric towards Tehran and said they are open to more talks on stabilising Iraq.

Washington has long accused Iran of fuelling sectarian violence in Iraq, notably by arming Shi'ite militias, an allegation it denies. Recently, the U.S. officials have been at pains to point out an apparent drop in attacks using Iranian munitions.

The two detainees accused of being "associates" of the Qods Force were among five Iranians captured in the northern city of Arbil in January on suspicion of arming and funding Shi'ite militias.

"All nine individuals were determined to no longer pose a security risk and to be of no continued intelligence value," the U.S. military said in a statement.

U.S. Defense Secretary Robert Gates denied a link between the release and a drop in roadside bomb attacks using weapons such as explosively formed penetrators (EFPs), which the United States accuses Iran of supplying.

"I continue to believe that it's too early to tell whether there really has been a decrease in Iranian supply of EFPs and other weapons into Iraq," he told reporters on his way back to Washington from a visit to Japan.

Attacks by Sunni militants in Iraq have also been in decline, after tribal leaders in several Sunni areas -- in particular the former militant stronghold of Anbar province -- banded together to drive out al Qaeda insurgents.

However, late on Friday, a suicide bomber wearing an explosive vest killed five local Sunni Arab tribal leaders meeting in a village in Diyala province northeast of Baghdad, police said. Those killed were members of the Diyala Salvation Council, a body set up to oppose al Qaeda in the province.

Among the dead was the deputy head of the Diyala Salvation Council, Sheikh Faeiz Lefta al-Obaidi.

"IRANIANS WERE INNOCENT"

Iranian Foreign Ministry spokesman Mohammad Ali Hosseini told Iran state radio that "American officials in Iraq admitted that the freed Iranians were innocent and they had no links with insurgents in Iraq".

Iraqi government spokesman Ali al-Dabbagh said the Iranians had been handed over to Iraqi Prime Minister Nuri al-Maliki and transferred to the Iranian embassy in Baghdad.

Iran's semi-official Mehr news agency said the nine, some of whom had been held for three years, landed at Tehran airport later on Friday.

Iranian state media identified the pair captured in Arbil as Mohammad Reza Asgari and Mousa Chegini. Asgari told Iranian television that U.S. forces had attacked their office in Arbil.

"We were their hostage for 10 months ... Our release shows that their accusations were baseless," Asgari said.

Iran says the "Arbil Five" are all diplomats and has called for them all to be released. Iranian media said the other seven freed on Friday were pilgrims. U.S. forces in Iraq are still holding 11 more Iranians in all.

The U.S. military has noted a sharp drop in mortar attacks on Baghdad's heavily fortified Green Zone last month. Many of those attacks have been blamed on Shi'ite militias using Iranian-made weapons.

The U.S. ambassador to Iraq, Ryan Crocker, has also taken note of the ceasefire ordered by Moqtada al-Sadr, head of the feared Shi'ite Mehdi Army, in August. U.S. officials accuse Sadr of having close links with Iran.

Crocker has held three rounds of talks with his Iranian counterpart this year on Iraqi security, helping to thaw a diplomatic freeze that lasted almost three decades. Last week, he said he expected another round of talks to take place soon. (Additional reporting by Waleed Ibrahim in Baghdad, Parisa Hafezi in Tehran and Andrew Gray; Editing by Andrew Dobbie)

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