Pakistani students returning from Iran on Thursday said they heard gunshots and stories of rioting and violence while being confined to campus and not allowed out of their dormitories in the evening.
Iran's leadership is trying to quell the worst domestic unrest since its 1979 revolution, with a rights group putting the death toll over 2,600.
As the protests swell, Tehran is seeking to deter US President Donald Trump's repeated threats to intervene on behalf of anti-government protesters.
"During nighttime, we would sit inside and we would hear gunshots," Shahanshah Abbas, a fourth-year student at Isfahan University of Medical Sciences, said at the Islamabad airport.
"The situation down there is that riots have been happening everywhere. People are dying. Force is being used."
Abbas said students at the university were not allowed to leave campus and told to stay in their dormitories after 4 p.m.
"There was nothing happening on campus," Abbas said, but in his interactions with Iranians, he heard stories of violence and chaos.
"The surrounding areas, like banks, mosques, they were damaged, set on fire ... so things were really bad."
Trump has repeatedly threatened to intervene in support of protesters in Iran but adopted a wait-and-see posture on Thursday after protests appeared to have abated. Information flows have been hampered by an internet blackout for a week.
"We were not allowed to go out of the university," said Arslan Haider, a student in his final year. "The riots would mostly start later in the day."
Haider said he was unable to contact his family due to the blackout but "now that they opened international calls, the students are getting back because their parents were concerned".
A Pakistani diplomat in Tehran said the embassy was getting calls from many of the 3,500 students in Iran to send messages to their families back home.
"Since they don't have internet connections to make WhatsApp and other social network calls, what they do is they contact the embassy from local phone numbers and tell us to inform their families."
Rimsha Akbar, who was in the middle of her final year exams at Isfahan, said international students were kept safe.
"Iranians would tell us if we are talking on Snapchat or if we were riding in a cab ... that shelling had happened, tear gas had happened, and that a lot of people were killed."
