Updated

A car loaded with explosives blew up near a bus carrying members of Iran's elite Revolutionary Guards in southeastern Iran on Wednesday, killing 11 of them and wounding 31. An Al Qaeda-linked Sunni militant group reportedly claimed responsibility.

The semi-official news agency Fars reported that the militant group Jundallah, or God's Brigade, issued a statement saying it carried out the blast. But officials did not confirm the claim, blaming "insurgents and drug-traffickers."

The bombing was the worst attack in years in the lawless corner of Iran near the Pakistan border, where drug gangs and militants have carried out attacks in the past.

Jundallah, God's Brigade, has been blamed for previous attacks on Iranian troops in the area. The group, which accuses Shiite-led Iran of discriminating against Sunni Muslim minorities in the southeastern region, also operates in Pakistan, where authorities have accused it of links to Al Qaeda.

The bombing came amid heightened tensions between the United States and Iran over the crises in Iraq and elsewhere in the Mideast. Iran has in the past accused the United States of backing militants in the southeast in order to stir up turmoil in the country. It has also cited such attacks — and bombings in a Sunni-dominated western part of the country — as evidence that Iran is a victim of terrorism.

The attack took place near Zahedan, the capital of Sistan-Baluchestan Province, when a car packed with explosives pulled to a stop in front of the bus at about 6:30 am, the official Islamic Republic News Agency reported. The car's occupants fled and seconds later the vehicle exploded, it said.

Eleven Revolutionary Guards were killed and 31 wounded in the attack, the provincial governor Hassan Ali Nouri told IRNA. He said one of the attackers was also killed in the blast, which he blamed on "elements of insecurity." The report corrected an earlier toll of 18 dead reported by IRNA.

State-run television said the bus had been taking the troops to work when the attack took place.

Hossein Ali Shahriyari, a deputy representing Zahedan, told an open session of the parliament Wednesday that "insurgents and drug traffickers" were behind the attack.

Shahriyari called lawless regions in southwestern Pakistan a safe haven for Iranian insurgents and drug traffickers and urged the Iranian government to take up the issue with Islamabad.

"Why doesn't our foreign diplomatic apparatus deal with Pakistan, whose soil has turned into a safe heaven for insurgents," he asked. His speech was broadcast live on state-run radio.

Soltan Ali Mir, a local Interior Ministry official, said five of those behind the explosion were arrested, IRNA reported. It did not say how many were involved.

"Two of the terrorists were arrested [immediately] after the attack. Police confiscated a camera and hand grenades from them. Later, three other terrorists behind today's bomb explosion were arrested," IRNA quoted Mir as saying.

Zahedan and its surroundings, which lie near Iran's borders with Pakistan and Afghanistan, have been the scene of clashes between police and drug smugglers in the past.

Three small explosions injured two people in Zahedan last June, but Wednesday's explosion was the deadliest in years.

In December, Jundallah claimed responsibility for the kidnapping of seven Iranian soldiers in the region, threatening to kill them unless Jundallah members held in Iranian prisons were released. Iranian security forces reported a month later that the seven had been freed — apparently by negotiations through local tribesmen.