Iran’s supreme leader has condemned the military intervention in Yemen by his country’s main regional rival, Saudi Arabia, describing it as “genocide”.
Ayatollah Ali Khamenei warned Riyadh that it would “not emerge victorious”.
A Saudi-led coalition launched an air campaign two weeks ago in an attempt to halt an advance by Houthi rebels and restore President Abdrabbuh Mansour Hadi, who fled the country last month.
On Wednesday, the US warned Iran over its alleged support for the rebels.
Secretary of State John Kerry said Washington would back any state that felt threatened by Iran and would not “stand by” if the Middle East were destabilised.
Shia power Iran has repeatedly denounced the air strikes launched by the coalition of nine, mostly Sunni Arab, countries to “defend the legitimate government” of Mr Hadi. But Ayatollah Khamenei’s comments were the most critical yet.
“The aggression by Saudi Arabia against Yemen and its innocent people was a mistake… It has set a bad precedent in the region,” he said in a televised speech.
“This is a crime and genocide that can be prosecuted in international courts,” he added. “Riyadh will not emerge victorious in its aggression.”
The World Health Organisation says at least 643 people have been killed and 2,226 wounded in Yemen since 19 March. Another 10,000 people have been driven from their homes.
Earlier on Thursday, Iranian President Hassan Rouhani called on countries in the region to work together to resolve the crisis.
The foreign ministry also summoned Saudi Arabia’s charge d’affaires in Tehran.
The state news agency, Irna, quoted the ministry as saying the envoy would be asked to explain “baseless accusations” made by a spokesman for the coalition.
On Wednesday night, Brig Gen Ahmed al-Assiri told a news conference that Iran had been training and equipping Houthi fighters, according to the Reuters news agency.
The US secretary of state also said that Iran’s support for the rebels was clear.
“There are obviously supplies that have been coming from Iran. There are a number of flights every single week that have been flying in,” Mr Kerry told PBS Newshour.
On Wednesday, Iran said it was sending two warships to the Gulf of Aden with the aim of “safeguarding naval routes”.
The coalition has so far failed to halt the advance into Aden by the Houthis and allied military units loyal to former President Ali Abdullah Saleh.
Mr Hadi left for Saudi Arabia at the end of March after the Houthis reached the southern port city, where he took refuge in February after fleeing Sanaa.
On Thursday, coalition warplanes reportedly bombed rebel positions and weapons depots in and around Sanaa.
The defence ministry building was among the targets, according to the AFP news agency.
Northern areas near the Saudi border and in the south around Aden were also hit.
Houthi fighters and allied soldiers meanwhile entered Ataq, the provincial capital of the mainly Sunni province of Shabwa after days of clashes with Sunni tribesmen.
“Ataq is like a military barracks. A tank here, an armoured vehicle there and non-stop patrols,” resident Saleh al-Awlaki told the Associated Press.
The rebels say their push into southern and eastern areas of Yemen is to combat militants from al-Qaeda in the Arabian Peninsula (AQAP).
On Thursday morning, residents of al-Siddah district in central Yemen told Reuters that AQAP flags were flying over local government offices, after Houthi rebels withdrew overnight.
Houthis – The Zaidi Shia Muslim rebels from the north overran Sanaa last year and then expanded their control. They want to replace Mr Hadi, whose government they say is corrupt. The US alleges Iran is providing military assistance to the rebels.
Ali Abdullah Saleh – Military units loyal to the former president – forced to hand over power in 2011 after mass protests – are fighting alongside the Houthis.
Abdrabbuh Mansour Hadi – The president fled abroad in March as the rebels advanced on Aden, where he had taken refuge in February. Loyal soldiers, Sunni Muslim tribesmen and Southern separatists have formed militia to fight the rebels.
Saudi-led coalition – A US-backed coalition of nine, mostly Sunni Arab states says it is seeking to “defend the legitimate government” of Mr Hadi.
Al-Qaeda in the Arabian Peninsula – AQAP opposes both the Houthis and President Hadi. A rival affiliate of Islamic State has also recently emerged.
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