Iranian troops arrested inside Pakistan

he exposure of what appeared to be a secret Iranian operation will further heighten tensions between the two countries. Relations have already been damaged after Iran claimed that a suicide bombing on its side of the border nine days ago was carried out by a militant group believed to have bases inside Pakistan.

Iran immediately sought to downplay the incident, claiming that the soldiers were border guards who had accidentally crossed into Pakistan while pursuing smugglers.

But there will be suspicion that the true reason for the operation is connected to an attack on the Iranian border town of Pishin on Oct 18 that killed 42 people, that Iran has linked to Britain, the United States and Pakistani intelligence.

The Iranian regime was particularly incensed that the casualties included 11 members of the Revolutionary Guard, five of whom were senior commanders including a general.

"It's a serious matter," a Pakistani security official was quoted as saying. "We are investigating why they crossed into our territory."

The bombings in Pishin were claimed by the Jundullah, a Sunni Muslim group that has carried out dozens of attacks in the region as part of its campaign to highlight what it claims is the marginalisation of Iran's Baluchi minority.

Iran was quick to suggest that Jundullah is received funding from Britain and the United States and logistical support from Pakistan's Intelligence Service.

Ayatollah Ali KhameneiAyatollah Ali Khamenei, Iran's supreme leader, gave those allegations his backing on Monday when he claimed that "foreign agents" were behind terrorist attacks in Iraq, Pakistan and parts of his country in an attempt to create discord between Shia and Sunni Muslims.

"Perpetrators of terrorist and bloody moves are directly or indirectly linked to foreign agents," Iran's Press TV quoted him as saying.

It is unclear how Pakistan will react to the cross-border incident. Already facing accusations that it has provided sanctuary to militants from Afghanistan and India, the government of Asif ZardariAsif Zardari, the Pakistani president, is keen not to alienate another neighbour.

Mr Zardari met Iran's interior minister in Islamabad at the weekend to discuss the bombing in Pishin and vowed to co-operate in capturing those involved in the attack.

Even so, he is likely to take a dim view of any unilateral Iranian action on Pakistani soil.