Former members of Tehran's powerful Revolutionary Guard have announced their readiness to fight in Iraq against the Islamic State, the official IRNA news agency reported. Iranian state TV quoted President Hassan Rouhani as saying his country will do all it can to battle terrorism next door.
"The Islamic Republic of Iran will apply all its efforts on the international and regional levels to confront terrorism," the report said Rouhani told al-Maliki by phone.
Iranian officials denied their forces were actively operating in Iraq, however.
Mansour Haghighatpour, who sits on an influential Iranian parliamentary committee on national security and foreign policy, told The Associated Press that Baghdad is capable of fighting the militants, but Tehran would consider other options if asked.
Iran has built close political and economic ties with postwar Iraq, and many influential Iraqi Shiites have spent time in the Islamic Republic. Iran this week halted flights to Baghdad because of security concerns and said it was intensifying security on its borders.
Police said Sunni militants driving machine gun-mounted pickups entered the two newly conquered Iraqi towns in Diyala province late Thursday — Jalula, 125 kilometers (80 miles) northeast of Baghdad, and Sadiyah, 95 kilometers (60 miles) north of the capital. Iraqi soldiers abandoned their posts there without any resistance, they said.
Jalula residents said the gunmen issued an ultimatum to the soldiers not to resist and give up their weapons in exchange for safe passage. After seizing the town, the gunmen announced on loudspeakers that they have come to rescue residents from injustice and that none would be hurt.
The gunmen later disappeared from Jalula, only to be replaced with the Kurdish security forces known as peshmerga. They raised the Kurdish flag over government buildings and transferred abandoned Iraqi military equipment back to the Kurds' self-ruled northern region, according to two police officials. The officials spoke on condition of anonymity because they were not authorized to talk to journalists, and the residents declined to give their names out of fears for their safety.
The Islamic State has vowed to march on Baghdad, but the capital would be a far more difficult target with its large Shiite population. The militants would face far stronger resistance from government forces and Shiite militias.
So far, they have stuck to the Sunni heartland and former Sunni insurgent strongholds where people are alienated by al-Maliki's government over allegations of discrimination and mistreatment.
Iraq's former Sunni vice president, Tariq al-Hashemi, told the AP in Istanbul that while the Islamic State was one player in the uprising, they are not the driving force.
"They are not involved in the decision-making," he said, adding that the Sunni tribes in Mosul and Anbar are "behind this Iraqi spring."
Baghdad considers al-Hashemi a fugitive after he was found guilty in absentia in terrorism-related cases — charges he dismisses as politically motivated.
Shiite cleric Muqtada al-Sadr and the Asaib Ahl al-Haq Shiite militia have vowed to defend Shiite holy sites, raising the specter of street clashes and sectarian killings.
Still, authorities have tightened security around the capital and residents stocked up on supplies.
Hundreds of young men volunteered for military service at a recruiting center Thursday, and more were being urged to join by cars playing Shiite religious songs that roamed Shiite neighborhoods Friday after the cleric's call.
The Islamic militants in Mosul declared they would impose Shariah law and trumpeted their success in a parade of seized armored vehicles that was captured on online video.
A fighter with a loudspeaker urged the people to join the militants "to liberate Baghdad and Jerusalem." The Islamic State's black banners adorned many of the captured vehicles. Some in the crowd shouted "God is with you" to the fighters.