Close allies and traditional adversaries of Lebanon paid tribute on Tuesday to the victims of massive and deadly twin blasts in Beirut, as condolences and offers of help poured in.

Lebanon's Prime Minister Hassan Diab called on "friendly countries" to support the country already reeling from its worst economic crisis in decades as well as the coronavirus pandemic.

Gulf nations were among the first to react, with Qatar promising to send field hospitals to support the medical response.

Qatar's ruler Emir Sheikh Tamim bin Hamad Al-Thani wished "a speedy recovery for the injured," while the United Arab Emirates' Vice President and ruler of Dubai, Sheikh Mohammed bin Rashid Al-Maktoum, tweeted "our condolences to our beloved people in Lebanon."

Kuwait said it would also send emergency medical aid.

Egypt expressed "deep concern" at the destruction, and Arab League chief Ahmed Aboulgheit offered condolences, stressing "the importance of finding the truth about the explosions".

Jordan's Foreign Minister Ayman Safadi said Amman was ready to provide any help Lebanon needed, while Iran said it was "fully prepared to render assistance in any way necessary".

"Our thoughts and prayers are with the great and resilient people of Lebanon," Iranian Foreign Minister Mohammad Javad Zarif tweeted.

"Stay strong, Lebanon."

Neighbouring Israel also offered humanitarian aid to Lebanon, with which it is still technically at war.

"Defense Minister Benny Gantz and Foreign Minister Gabi Ashkenazi, on behalf of the State of Israel, have offered the Lebanese government -- via international intermediaries -- medical and humanitarian aid, as well as immediate emergency assistance," a statement read.

Outside the region, President Vladimir Putin said that "Russia shares the grief of the Lebanese people," according to a Kremlin statement.

"I ask you to convey words of sympathy and support to the families and friends of the victims, as well as wishes for a speedy recovery to all affected."

Washington said it too would help.

"We extend our deepest condolences to all those affected, and stand ready to offer all possible assistance," a State Department spokesperson said.

French Foreign Minister Jean-Yves Le Drian said the country was "ready to provide assistance according to the needs expressed by the Lebanese authorities".