BEIJING — China on Friday appealed for restraint from all sides, "especially the United States", after top Iranian commander Qasem Soleimani was killed in a US strike in Iraq.

The Pentagon said President Donald Trump ordered Soleimani's "killing," after a pro-Iran mob this week laid siege to the US embassy in Baghdad.

Iran's supreme leader Ayatollah Ali Khamenei vowed to take "severe revenge" after Soleimani was killed when a volley of missiles hit Baghdad's international airport, striking a convoy belonging to the Hashed Al-Shaabi, an Iraqi paramilitary force with close ties to Tehran.

"China has always opposed the use of force in international relations," Chinese Foreign Ministry spokesman Geng Shuang said at a daily press briefing.

"We urge the relevant sides, especially the United States, to remain calm and exercise restraint to avoid further escalating tensions," Geng said.

He said Iraq's sovereignty, independence and territorial integrity must be respected.

China, a permanent member of the UN Security Council, is a key partner of Iran and major buyer of the country's oil.

Geng said China urged all sides to abide by the principles of the UN charter and the "basic norms of international relations".

Iran, China and Russia held joint naval drills in the Indian Ocean and the Gulf of Oman last week and the Iranian foreign minister visited Beijing earlier this week.

China and Russia are also parties to the 2015 nuclear deal with Iran, from which Trump withdrew in May last year.

Meanwhile, Moscow warned Friday that the US killing of top Iranian commander Soleimani in Iraq would boost tensions across the Middle East.

"The killing of Soleimani... was an adventurist step that will increase tensions throughout the region," news agencies RIA Novosti and TASS quoted the Foreign Ministry as saying.

Konstantin Kosachev, the head of the foreign affairs committee of the Russian parliament's upper house, said Soleimani's killing was a mistake that would hit back at Washington.

"Retaliatory strikes will certainly follow," he said in a post on his Facebook page, adding that Israel was likely also worried.

He said the killing marked the end of any chance to salvage the nuclear deal.

"The last hopes of resolving the Iranian nuclear problem have been 'bombed'," he wrote.

In Paris, "the US killing of a top Iranian military commander has made the world "more dangerous," France's Europe minister said Friday, calling for efforts to de-escalate the deepening conflict in the Middle East.

"We have woken up to a more dangerous world," Amelie de Montchalin told RTL radio, saying President Emmanuel Macron would consult soon with "players in the region."

"In such operations, when we can see an escalation is under way, but what we want above all is stability and de-escalation," Montchalin said.

"All of France's efforts... in all parts of the world aim to ensure that we are creating the conditions for peace or at least stability," she added.

"Our role is not to take sides, but to talk with everyone," Montchalin said. — AFP