(Refiles story to change dateline to March 5)
By Saleem Ahmed and Asif Shahzad
QUETTA, Pakistan, March 5 (Reuters) - Pakistanis fleeing Iran described explosions and missile strikes across Tehran shaking the ground under their feet and engulfing buildings in fire and smoke in a city emptied of many of its residents.
The conflict has widened sharply, with a U.S. submarine sinking an Iranian warship off Sri Lanka on Wednesday and NATO air defences destroying an Iranian missile fired towards Turkey.
Governments have been scrambling to evacuate stranded citizens, with most of the region's airspace closed due to the risk of missiles hitting passenger planes.
"I was in the classroom when a powerful explosion rocked our university building," Hareem Zahra, 23, a student at the Tehran University of Engineering, told Reuters after crossing Pakistan's land border with Iran.
"We saw thick smoke coming from many buildings on fire," she said, adding Tehran was under attack until the moment she left.
TEHRAN LOOKED DESERTED
Nearly 1,000 students, businessmen and pilgrims have fled Iran since the war started out of a total 35,000 Pakistanis in the country, Mudassir Tipu, Pakistan's ambassador to Tehran, said.
"There are now serious challenges. As you know there is no internet in most parts of Iran," he said.
Iran has retaliated with a barrage of ballistic missiles targeting Israel and Washington's allies in the Gulf, including Qatar, Kuwait, the UAE, and Saudi Arabia, following U.S. and Israeli air strikes that killed Supreme Leader Ayatollah Ali Khamenei on Saturday.
Tehran has looked deserted since the conflict began, said Nadir Abbas, 25, a student of Persian literature at a university in the Iranian capital.
"I saw a drone hit a basketball court where six girl players lost their lives."
Reuters could not verify his account.
'DESTRUCTION EVERYWHERE'
Islamabad is walking a diplomatic tightrope as it attempts to maintain warming ties with Washington while expressing solidarity with Iran.
Pakistan is home to the second-largest Shi'ite population in the world after Iran and being drawn into the conflict could lead to instability at home as well as complications evacuating its citizens.
"The first attack happened right next to my hospital," said Sakhi Aun Mohammad, a student at Tehran University of Medical Sciences.
After he reached the border, an Iranian friend called to check if he was safe, saying: "'Thank God, you have gone to Pakistan, all of you are safe, but your hostel has been attacked'".
A Pakistani diplomat who is still in Tehran said attacks took place every four or five hours, adding one missile struck a building next to his office.
"At times you will feel as if something exploded right at your feet," he said.
"The last time I got out was at night. Buildings had collapsed, some others were on fire. There is destruction everywhere."
He added: "It is almost like a ghost town."
(Reporting by Saleem Ahmed in Quetta and Asif Shahzad in Islamabad; Editing by Saad Sayeed)
