British Prime Minister Boris Johnson met with oil-rich Saudi Arabia's de facto ruler Crown Prince Mohammed bin Salman to lobby for higher production on Wednesday after Russia's invasion of Ukraine sent markets into turmoil.

Johnson, one of the few Western leaders to visit Riyadh since the 2018 murder of journalist Jamal Khashoggi in the Saudi consulate in Istanbul, spoke with Prince Mohammed after talks with Abu Dhabi Crown Prince Mohammed bin Zayed in the United Arab Emirates.

The UK leader is hoping the oil-rich Gulf states will raise production to help calm oil prices, which soared to nearly $140 a barrel before dropping below $100, and help end the West's dependency on Russian oil following the invasion.

His visit coincides with fresh condemnation of Saudi Arabia's human rights record after 81 people were put to death in a mass execution on Saturday. Rights groups questioned whether they had received fair trials.

Also in the region during Johnson's visit, British-Iranians Nazanin Zaghari-Ratcliffe and Anoosheh Ashoori were released after years in detention in Iran on charges of plotting to overthrow the government and spying for Israel, respectively.

Their families believe they were held as political prisoners until the UK settled a £400-million ($520 million, 475 million euro) debt for defence equipment dating back to the time of the shah of Iran.

In their talks, Johnson and Prince Mohammed discussed "regional and international issues of common interest and efforts exerted in their regard, including the developments in Ukraine", the official Saudi Press Agency said, without mentioning any talks on oil.

Johnson met Prince Mohammed after discussing "the stability of the global oil markets" with Emirati royal Sheikh Mohammed, according to the UAE's official WAM news agency.

"The leaders welcomed the long-standing partnership between our two countries and discussed opportunities to increase collaboration between the UK and UAE on energy security, green technology, and trade," a Downing Street spokesperson said.

Before leaving for Riyadh, Johnson promised to raise human rights issues with Prince Mohammed, but he also stressed Britain's "very important relationship" with the oil-rich Gulf.

"It's not just a question of looking at the OPEC countries and what they can do to increase supply, though that is important," Johnson told British media.

"When we look at the dependency the West in particular has built up on Putin's hydrocarbons, on Putin's oil and gas, we can see what a mistake that was because he's been able to blackmail the West."

- 'Putin's addiction' -

Johnson's spokesman said he would also ask Prince Mohammed to condemn Russia's President Vladimir Putin over the assault on Ukraine. 

Saudi Arabia and the UAE, which are two of the world's biggest oil exporters and both have ties to Moscow, have so far avoided taking a position against Russia.

But Johnson said before leaving that the impact of Putin's "brutal and unprovoked" assault will be felt far beyond Europe.

He said as Western sanctions begin to bite, a new international coalition was needed to offset their impact on consumers already feeling the pinch from rising inflation.

"The world must wean itself off Russian hydrocarbons and starve Putin's addiction to oil and gas," he said in a statement.

"Saudi Arabia and the United Arab Emirates are key international partners in that effort."

The UAE and Saudi Arabia are the UK's two largest economic partners in the region, with bilateral trade worth £12.2 billion and £10.4 billion respectively in 2020, Johnson's office said.

Russia is the world's largest producer of gas and one of the biggest oil producers.

Like the United States, Britain plans to phase out Russian oil imports by the end of the year, as part of wide-ranging sanctions targeting Russian businesses and billionaires.

US President Joe Biden and Prince Mohammed haven't spoken since Biden took office and vowed to treat the kingdom as a "pariah" state over Khashoggi's killing, which the CIA blamed on the Saudi royal.

Torbjorn Soltvedt, Middle East and North Africa analyst at Verisk Maplecroft, said that "without this rift, it is unlikely Johnson would now be spearheading oil diplomacy efforts in the Gulf".

He said the odds were "stacked against Johnson" in changing Saudi oil policy, but that the UAE "may be more willing to open the taps" as it wants to capitalise on its oil reserves more quickly.

But the UAE on March 10 reaffirmed its commitment to OPEC+ alliance agreements to stick to existing output targets through April.