Yemen's Houthi group said on Wednesday it had identified dozens of sites in the United Arab Emirates as possible targets, in an attempt to underscore its military clout following a weekend attack it claims to have carried out on Saudi oil facilities.

At a weapons exhibition in July in Yemen's Houthi-controlled capital Sanaa, military officials whipped silken sheets off what they said were newly-developed drones and missiles.

The U.S. State Department called on American citizens to "exercise increased caution" while travelling to Saudi Arabia, a travel advisory posted on its website said on Wednesday.

Saudi Arabia has shut down its crude oil pipeline to Bahrain after attacks on Saudi oil facilities, two trade sources told Reuters on Monday.

The Bahraini Ministry of Foreign Affairs said that it "strongly condemns the terrorist attack that targeted two Aramco oil facilities in Buqayq and Hijrat Khurais in the Kingdom of Saudi Arabia."

Oil prices surged more than 15% at the open on Sunday after an attack on Saudi Arabia's oil facilities on Saturday that knocked out more than 5% of global oil supply.

Amnesty International has called on Saudi Arabia to reveal the whereabouts of a Qatari father and son who allegedly disappeared during a visit to the kingdom last month, the rights group said in a letter published on Tuesday.

Saudi Arabia called on southern Yemeni separatists on Thursday to cede control of Aden and voiced its support for the government, an indication that its rift with close ally United Arab Emirates had deepened.

Washington is in talks with Yemen's Iran-aligned Houthi rebels in a bid to end the country's war, a top US official said on Thursday, the first such contact in more than four years.

Yemeni government officials have begun indirect talks with United Arab Emirates-backed southern separatists in the Saudi Red Sea city of Jeddah to end fighting in Aden and other southern provinces, a Yemeni official said on Wednesday.

Saudi Arabia has deployed more troops in southern Yemen to try to contain clashes between nominal allies in the Saudi-led military coalition fighting the Houthis that risk further fragmenting the country.

The United States, Britain and France may be complicit in war crimes in Yemen by arming and providing intelligence and logistics support to a Saudi-led coalition that starves civilians as a war tactic, the United Nations said on Tuesday.

Saudi Arabia is struggling to hold together a military coalition fighting Iran-aligned Houthis in Yemen after local allies turned on each other in a power struggle that has strained Riyadh's alliance with its main regional partner, the United Arab Emirates.

The United Arab Emirates carried out air strikes against government forces in South Yemen on Thursday in support of southern separatists who have deployed reinforcements to take back control of the port of Aden from their supposed allies in the Saudi-led coalition.

Yemeni President Abd-Rabbu Mansour Hadi said on Thursday that government forces had withdrawn from Aden to prevent the city from being destroyed, according to state news agency SABA .

Saudi Arabia and the United Arab Emirates (UAE) have looked inseparable on the world stage, working together to project power in the Middle East and beyond, and courting U.S. President Donald Trump to counter common foe Iran.

Saudi Arabia has begun allowing adult women to travel without permission and to exercise more control over family matters, state news agency SPA reported on Tuesday, following a flurry of royal decrees approving the changes.

The president of Yemen's Southern Transitional Council (STC) headed with a delegation to the Saudi city of Jeddah on Tuesday after accepting the kingdom's invitation to a summit on the crisis in the Yemeni port city of Aden, the council said.

The refusal of Yemeni southern separatists to hand back control of Aden port has delayed a summit in Saudi Arabia that is due to discuss reshuffling Yemen's ousted government to include the separatists and end the stand-off, three Yemeni sources said.

Saudi Minister of Energy Khalid Al-Falih said on Saturday that Shaybah oilfield was targeted by explosive-laden drones.