Saudi Arabia and the United Arab Emirates, both allies of Washington, are also vulnerable to Iranian counter strikes, analysts say.
In September, US officials blamed Iran for a missile and drone attack on oil installations of Saudi Aramco, the Saudi state energy giant and world's largest oil exporter
All you need to know about the Iranian Major-General killed by the US in an air strike ordered by President Donald Trump at Baghdad airport
"We are at a dangerous point of escalation. It is now important through prudence and restraint to contribute to de-escalation," said Chancellor Angela Merkel's spokeswoman Ulrike Demmer
"Following the martyrdom of the glorious general haj Qasem Soleimani, I name Brigadier General Esmail Qaani as the commander of the Quds Force"
Here are some reactions to the killing of Iranian Major-General Qassem Soleimani
We will take revenge from all those involved and responsible for his assassination, Amir Hatami said
Qassem Soleimani and Abu Mahdi al-Muhandis were killed late on Thursday
Soleimani was the key architect of Iran's regional influence, leading the fight against jihadist forces and extending Iran's diplomatic heft in Iraq, Syria and beyond
The death of Qasem Soleimani, who led the Revolutionary Guards' Quds force, heightened fears of an armed conflict between the U.S. and Iran that could easily pull in other countries.
Trump spoke with Abdel Mahdi earlier by telephone, stressing the need to protect Americans and US facilities in Iraq, the White House said.
Fifteen fighters were killed by the US strikes in western Iraq, while several were wounded, according to an official from the Tehran-backed Hashed al-Shaabi paramilitary force.
If we are back where we started the decade, we know the task, we have the tools - and like the protesters, we know the value of sticking to it
Friction between Tehran and Washington has increased since last year when US President Donald Trump pulled the United States out of Tehran's 2015 nuclear deal
Jaishankar is also expected to call upon Iranian President Hassan Rouhani, the External Affairs Ministry said in a statement on Saturday
Since May, Iran has taken a series of measures, including stepping up uranium enrichment, in breach of the 2015 deal, with another such move likely in early January
"Iran supports (a) majority decision about dropping oil production," said Hossein Kazempour Ardebili, Iran's representative to OPEC
Till September this year, Iran outpaced Russia and CIS both in terms of volume and value of tea shipments from India
Amnesty said there had been dozens of deaths in the Tehran suburb of Shahriar, likely one of the areas with the highest toll of those killed in the unrest
We are sanctioning Iran's Minister of Information and Communications Technology for restricting internet access, said treasury secretary