QUETTA: Pakistani authorities on Tuesday released 11 Iranian Revolutionary Guards detained a day earlier for trespassing into Pakistani territory, officials said.

The guards were arrested in the Mashkhel area on the border with Iran eight days after a suicide bomber killed 42 people, including six Revolutionary Guard commanders, in Iran's southeastern Sistan-Baluchestan province.

Fars news agency, without quoting a source, said the group was handed over by the Pakistani army to the Iranian border guards at Mirjaveh border crossing in the restive Iranian province of Sistan-Baluchestan.

A spokesman for Pakistan's paramilitary Frontier Corps told AFP that a group of Iranians was Tuesday handed back at the border.

'We can confirm only that yesterday we had some Iranians who entered Pakistan by mistake and today that we handed them over to Iranian officials at the Pakistani border,' said the spokesman Murtaza Baig.

Another Pakistani border official had said late Monday that 11 Iranian Revolutionary Guards were arrested after they crossed the border into Pakistan, but he spoke on condition of anonymity and there was no other confirmation.

Iran said those responsible for the attack were based in Pakistan and demanded that the government in Islamabad hand over Abdolmalek Rigi, the leader of the Sunni rebel group Jundallah (Soldiers of God).

Islamabad has strongly denied that the Jundallah attack was launched from its territory.