A senior Iranian commander warned the United States that a "fire might start" over an aid ship bound for Yemen on Wednesday after the Pentagon urged it to change course.

Brigadier General Masoud Jazayeri said it was Iran's right to deliver relief supplies to Yemen as a humanitarian ceasefire takes hold and rejected Washington's request that aid be taken instead to a United Nations hub to allay worries the cargo might be military.

The United Nations cultural agency on Tuesday condemned "severe damage" caused to heritage sites in Yemen, such as Sanaa's old city, during intense bombing of the rebel-held capital.

"I condemn these destructions and I call on all parties to keep cultural heritage out of the conflict," said UNESCO director general Irina Bokova.

A technical fault or human error caused the crash of a Moroccan warplane in Yemen, the Saudi-led coalition said on Tuesday, denying rebel fire was responsible.

Yemen's Shiite Huthi rebels said on Monday that they shot down a coalition warplane at the weekend, shortly after Morocco reported one of its fighters missing on a sortie.

Saudi Arabia on Tuesday carried out its 80th beheading of the year, edging closer to the 87 executions it carried out during all of 2014, according to Agence France Presse tallies.

The interior ministry said a Saudi citizen, Rabie al-Sai'ari, had been convicted of trying to smuggle hashish into the kingdom.

Kuwait has requested arbitration in a dispute with Saudi Arabia over shared oil production from the neutral zone between the Gulf neighbors which has completely halted, a newspaper reported Tuesday.

Kuwaiti daily Al-Jarida said that talks between the two governments on output from the 5,000 square kilometer (1,930 square mile) zone that they exploit jointly under a half-century-old treaty had reached deadlock.

A Saudi-set humanitarian truce is poised to take effect in Yemen late Tuesday, after 24 hours of intensive bombing by a military coalition led by the kingdom targeting Iran-backed rebels.

The five-day ceasefire -- scheduled to start at 11:00 pm (2000 GMT) -- aims to allow deliveries of desperately needed relief supplies, although aid groups have already warned they need more time.

Discontent with American policy toward Iran is behind the last-minute pullout by Saudi King Salman from a summit with U.S. President Barack Obama this week, analysts say.

Obama invited Salman along with five other Gulf rulers to the White House on Wednesday followed by a retreat the following day at Camp David.

Saudi Arabia's new foreign minister insisted Monday that King Salman's last minute decision not to attend a Camp David summit was not intended as a snub to the United States.

"This is not related in any way, shape or form to any disagreement between the two countries," Foreign Minister Adel al-Jubeir told reporters at Saudi Arabia's embassy Washington.

A Pakistani and a Saudi were killed on Monday when the Saudi Arabian border region came under renewed bombardment from Yemen, official media reported.

The Pakistani's killing was a rare death of a foreigner during weeks of war the United Nations says have killed more than 1,400 people in Yemen.

Discontent with American policy toward Iran is behind the last-minute pullout by Saudi King Salman from a summit with U.S. President Barack Obama this week, analysts said.

Obama invited Salman along with five other Gulf rulers to the White House on Wednesday followed by a retreat the following day at Camp David.