Iran's interior minister has warned it may send forces into Pakistan if it does not act to free five Iranian border guards seized 10 days ago.
The men are thought to have been taken into Pakistan after being captured in Iran's Sistan Baluchistan region.
Abdolreza Rahmani-Fazli demanded that Islamabad treat the case "strongly and seriously" and "take the necessary measures" to secure their release.
The Sunni militant group Jaish al-
Adl has said it was behind their capture.
The group has posted what it said were photographs of the guards, bound and being held in an unknown location.
A video broadcast by al-Arabiya TV on Friday purportedly showed one of the men, Sgt Jamshyd Danaifard, saying they were "safe and sound".
He added that Jaish al-
Adl wanted the Iranian authorities to exchange 300 Sunni prisoners in Iran and its close ally Syria for the guards.
'New security sphere'
The day after the capture of the guards on 8 February, the Iranian foreign ministry reportedly summoned Pakistan's charge d'affaires to demand that Islamabad "act firmly against the leaders and members of the terrorist group who have fled into Pakistan".
On Monday, Mr Rahmani-Fazli told state TV that Iran had "asked Pakistan to deal with the issue strongly and seriously".
Otherwise, he said, Pakistan must "allow Iran to maintain the security of the region deep on Afghanistan and Pakistan soil".
"We are expecting a proper and precise answer. Otherwise we do consider it our own right to intervene and create a new security sphere for our safety."
The Isna news agency reported separately that an Iranian delegation had travelled to Pakistan on Monday to try to secure the guards' release.
The deputy chief-of-staff of Iran's armed forces meanwhile told the Fars news agency that "political and military measures are under way to set them free".
Sistan Baluchistan, which borders both Afghanistan and Pakistan, has been the scene of frequent clashes in recent years between Iranian security forces and drug smugglers and Sunni rebel groups.
In October, Jaish al-
Adl said it was behind the killing of 14 Iranian border guards and the capture of three others in Sistan Baluchistan.
The authorities in the provincial capital, Zahedan, responded by hanging 16 people they claimed were "linked to groups hostile to the regime".
In November, Jaish al-
Adl shot dead a local prosecutor and his driver. The next month, a bomb blast killed three Revolutionary Guards.
