Iran warned its citizens, particularly scientists, on Tuesday not to visit America, saying Iranians there were subjected to arbitrary and lengthy detention in inhuman conditions, Reuters reports.

"Iranian citizens, particularly elites and scientists, are requested to seriously avoid traveling to America, even to take part in scientific conferences and even having an invitation," a travel advisory on the foreign ministry website said.

It cited, "America's cruel and one-sided laws toward Iranians, especially Iranian elites, and arbitrary and lengthy detention in completely inhuman conditions" as reasons for the travel advisory.

The United States and Iran on Saturday swapped prisoners - American graduate student Xiyue Wang, detained for three years on spying charges, and imprisoned Iranian stem-cell researcher Massoud Soleimani, accused of sanction violations - in a rare act of cooperation between two longtime foes.

Soleimani was arrested upon arrival in the U.S. last year after being invited to take part in a research program at the Mayo Clinic in Minnesota, according to the semi-official Fars news agency.

Several dozen other Iranians are being held in U.S. prisons, many of them for breaking sanctions.