Pakistan warned Iran on Tuesday not to send troops across the two countries' shared border to retrieve five kidnapped Iranian border guards, an incident that threatens to exacerbate regional and sectarian tensions.

On Monday, Iranian Interior Minister Abdolreza Rahmani-Fazli was quoted as saying Iran might consider sending its forces onto Pakistani soil if Pakistan did not take the steps necessary to fight against militants.

"Iranian forces have no authority to cross our borders in violation of the international law. We must respect each other's borders," the Pakistani government statement said.

Predominantly Shi'ite Iran says militants seized the guards about 5 km inside Iran on February 6 in the province of Sistan-Baluchistan and took them into Pakistan.

A Sunni insurgent Iranian group calling itself Jaish Al-Adl (Army of Justice) claimed responsibility for the kidnapping, according to a Twitter account purporting to belong to the group. Its authenticity could not be immediately verified.

"The government of Pakistan regrets the suggestions of negligence on its part over the incident, especially when Pakistan's active support against terrorists groups in the past, is well-known and acknowledged by Iran," the Pakistani statement said.

Pakistan said it was in contact with Iran and had searched the area looking for the abducted border guards but been unable to find them in the mountainous, sparsely populated area.

The area where the kidnappings took place has a history of violence and sectarian problems.

Both countries are Muslim, but Pakistan is a majority Sunni state with a minority of Shi'ites. Iran is the reverse. In both countries, the minority sect complains of discrimination. - Reuters