Thousands of protesters in war-torn Syria's rebel enclave of Idlib on Tuesday marked 11 years since the start of an anti-government uprising, buoyed by the global outcry over Russia's invasion of Ukraine.

Gathered on the main square in the northwestern city of Idlib, more than 5,000 people took part in one of the largest rallies the beleaguered region has seen in months.

Many of the demonstrators hoped the war launched by the Syrian government's main backer Russia in Ukraine would rekindle interest in their cause.

Gulf Arab countries are seeking to host rare talks between Yemen's warring parties, including the Iran-backed Huthi rebels, in Riyadh at the end of the month, officials said on Tuesday.

Yemen, the Arab world's poorest country, has been wracked by a devastating war since 2014, pitting the Huthis against the internationally recognised government.

Repeated diplomatic efforts to get the two sides to agree a peace deal have failed over the years.

Iran has arrested several suspected members of a spy network linked to arch foe Israel, foiling its attempt to sabotage a key underground nuclear facility, state media reported.

The announcement comes as Iran is engaged in talks with major powers on reviving a landmark nuclear deal abandoned by the United States in 2018.

Iran has accused Israel of repeatedly targeting its nuclear facilities and scientists, most recently in an attempt to undermine efforts to restore the 2015 agreement, which was bitterly opposed by the Jewish state.

Russia has drawn up lists of 40,000 fighters from Syrian army and allied militias to be put on standby for deployment in Ukraine, a war monitor said Tuesday.

The Kremlin said last week that volunteers, including from Syria, were welcome to fight alongside the Russian army in Ukraine.

The Syrian Observatory for Human Rights and activists said Russian officers, in coordination with the Syrian military and allied militia, had set up registration offices in regime-held areas.

Israeli troops killed two Palestinians in separate shootings in the occupied West Bank Tuesday, the latest in a flurry of deadly clashes as a US envoy tours the region seeking to ease tensions.

A 16-year-old died in an exchange of fire with troops carrying out an arrest raid outside the northern city of Nablus, the Palestinian health ministry and Israeli security forces said.

Separately, a Palestinian in his 20s was killed in Qalandia outside Jerusalem, the health ministry said.

Oil prices plunged on Tuesday as major crude consumer China placed nearly 30 million people under Covid lockdown and traders tracked the latest developments in Ukraine and Iran nuclear talks.

Hong Kong and Chinese mainland stock markets closed sharply lower while European equities finished in the red.

Wall Street, however, was higher in midday deals.

Crude futures slumped under $100 per barrel just a week after benchmark contract Brent North Sea soared to a 14-year high close to $140 following Russia's invasion of Ukraine.

The government in Kyiv continues to function, the banking system is stable and debt payments are viable in the short term, but the Russian invasion could plunge Ukraine into a devastating recession, the IMF said Monday.

The Washington-based crisis lender also warned the war could have broader repercussions, including by threatening global food security by causing prices to rise and hampering the planting of crops, especially wheat.

Iranian Foreign Minister Hossein Amir-Abdollahian will head to Moscow on Tuesday, his ministry said, days after negotiations to salvage the Iran nuclear deal stalled amid new Russian demands.

"Russia has made its official demands loud and clear, and this needs to be discussed among all parties to the 2015 agreement, like all the demands that have been presented by other parties," foreign ministry spokesman Saeed Khatibzadeh told reporters on Monday.

The number of people in war-torn Yemen starving in famine conditions is projected to increase five-fold this year to 161,000, UN agencies warned Monday, amid fears of a dire shortfall of life-saving aid.

Over 30,000 people are already struggling in famine conditions, a joint statement by the UN's Food and Agriculture Organization (FAO), UN children's fund UNICEF and the World Food Programme (WFP) said.

Art Dubai, the Middle East's largest annual contemporary art fair, has featured for the first time digital works, as the wealthy Gulf emirate seeks to position itself as a crypto-assets hub.

This year, in its 15th edition, the three-day fair hosted more than 100 local and foreign art dealers, with an entire wing of 17 galleries and platforms dedicated to showcasing and selling NFTs, or non-fungible tokens.