Kosovo President Vjosa Osmani and Prime Minister Albin Kurti also expressed their "heartfelt" condolences.
Meanwhile, Qatar's Emir Sheikh Tamim bin Hamed Al Sani called President Erdoğan and conveyed sympathies to those who lost their lives.
Palestinian President Mahmud Abbas also expressed his condolences and condemned the explosion.
Israeli President Isaac Herzog was also among the world leaders conveying condolences. "The whole world should take a common and determined stance against terrorism," he said.
Libyan Prime Minister Abdulhamid Dibeybe said they stand in solidarity with Türkiye.
Messages of condolence were also sent by EU foreign policy chief Josep Borrell, President of the European Council Charles Michel, German President Frank-Walter Steinmeier and Italian Prime Minister Giorgia Meloni.
NATO Secretary General Jens Stoltenberg said: "Shocking images from Istanbul. My thoughts and deepest condolences to all those affected & to the Turkish people. #NATO stands in solidarity with our Ally Türkiye."
French President Emmanuel Macron said the Turkish people were struck in their heart, Istanbul.
"On this day so symbolic for our nation, while we think of the victims who fell on November 13, 2015, the Turkish people are struck by an attack in their heart, Istanbul. To the Turks: we share your pain. We stand with you in the fight against terrorism," Macron tweeted.
On Nov. 13, 2015, terrorists carried out a set of coordinated attacks in Paris, killing 130 people.
Meanwhile, the US also condemned the attack. "The United States strongly condemns the act of violence that took place today in Istanbul, Türkiye," said a statement by Karine Jean-Pierre, White House press secretary.
"Our thoughts are with those who were injured and our deepest condolences go to those who lost loved ones. We stand shoulder-to-shoulder with our NATO Ally Türkiye in countering terrorism," it added.
The foreign ministries of Pakistan, Jordan, Egypt, Saudi Arabia, Germany, India, Bosnia and Herzegovina and Greece also expressed condolences.
The Gulf Cooperation Council and President of Bosnia and Herzegovina's Republika Srpska entity Milorad Dodik also condemned the attack.
According to Istanbul Governor Ali Yerlikaya, the blast occurred at around 4.20 p.m. local time, with police and emergency officials cordoning off the scene.
Turkish President Recep Tayyip Erdoğan said that according to the initial information, the explosion could be a suspected act of terrorism and a woman played a role in it. "It smells like terrorism," he told a news conference before leaving for a G20 summit in Bali, Indonesia.
