The Swiss embassy in Tehran has tightened its security over recent weeks due to "higher risks", according to the foreign ministry.
The statement followed a report by the Südostschweiz am Sonntag newspaper, which alleged that there were "definite threats" against the Swiss delegation in Iran.
"Security measures have been stepped up over the past few weeks at the embassy," foreign ministry spokesman Jean-Philippe Jeannerat confirmed on Sunday.
Jeannerat added that since the Lebanon crisis in July all Swiss delegations in the Middle East had undergone a security review, which revealed that certain delegations face higher risks and security needs to be improved, including in Iran.
He declined to comment on the Südostschweiz am Sonntag article, which stated that the terrorist movement al-Qaeda had Swiss ambassador to Tehran, Philippe Welti, on its list of potential targets.
He added that the foreign ministry had no plans to recall its ambassador from the Iranian capital.
Switzerland represents the interests of Washington in Iran, as the two states have not held direct diplomatic relations since the 1979 American hostage crisis in Tehran. It also ensures diplomatic and consular contacts between both countries.
Südostschweiz am Sonntag said the threats against the Swiss embassy in Tehran were set against a backdrop of growing tensions between Iran and the US over the ongoing Iran nuclear crisis.
Iran has said it will not yield to international pressure and maintains it has a right to a nuclear programme which it says is for civilian purposes. But many western countries have doubts about Iran's real intentions, fearing the country wants nuclear weapons.
According to the former Swiss ambassador to Tehran, Tim Guldimann, there is no immediate solution in sight to the crisis over Tehran's nuclear programme and the international community is now pursuing two tracks - dialogue and possible sanctions.
Six world powers agreed on October 6 to discuss possible UN Security Council sanctions to punish Iran for failing to halt its nuclear programme but said they were still open to negotiations with Tehran.
swissinfo with agencies
Iran opened an embassy in Bern in 1917.
In 1919 Switzerland opened a consulate general in Tehran.
Since 1981 Switzerland has represented US interests in Iran.
In 2005 there were 187 Swiss citizens living in Iran.
At the end of 2004, 3,801 Iranians were living in Switzerland.
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