Twelve Iranian engineers and five of their Afghan colleagues were kidnapped by Taliban gunmen on Monday in a remote region of Afghanistan near its border with Iran, local officials and the Iranian government said.
The men, who were working on a road construction project, were snatched at gunpoint in the Post-i-Road district of Farah province, which borders Iran, provincial government spokesman Naqibullah Farahi told AFP.
Tehran confirmed the abduction of 12 Iranians, while the Afghan provincial authorities had earlier said the number was ten.
"We are closely following the issue," said Ramin Mehmanparast, spokesman for the Iranian Ministry of Foreign Affairs, quoted by the website of Iran's state broadcaster.
The Afghan embassy in Tehran will press the "Kabul authorities to exercise their responsibilities with regard to Iranian nationals and to take firm and swift action on this kidnapping," he added.
Taliban spokesman Yusuf Ahmadi told AFP by telephone that the insurgent group had no knowledge of the kidnapping, although the rebels have been responsible for similar abductions in the past.
Iranian foreign ministry spokesman Ramin Mehmanparast said the Afghan authorities had been asked to take "firm and swift action" on the abductions, the state television website reported.
Farah is a remote province which borders Iran and faces significant Taliban activity.
The abduction is the latest in a series of kidnappings of Afghan and foreign nationals in Afghanistan since a US-led invasion ousted Taliban in 2001.
Most hostages are released unharmed following negotiations, but last December a Bangladeshi road worker was killed during a kidnapping in northern Afghanistan. Five of his colleagues remain in captivity.
Two French journalists from state-owned channel France 3 remain in captivity after being kidnapped east of Kabul in December 2009 by suspected Islamist insurgents.
There are around 130,000 international troops in Afghanistan fighting the Taliban and other insurgents.