Shiite rebels in Yemen claim to have shot down a Moroccan F-16 fighter jet taking part in a Saudi-led coalition targeting them and their allies in the Arabian Peninsula nation.
Morocco's military, however, only would say that the jet had gone missing at around 6pm local time on Sunday.
The purported downing of the jet fighter came as a Saudi-owned news channel, al-Hadath, aired live footage of tanks and armoured personnel carriers loaded onto giant trucks, saying they were part of a "strike force" deploying to the kingdom's border with Yemen.
There have been no signs to suggest that a ground offensive was imminent, although the coalition has not ruled one out.
Photos purporting to show the wreckage of the Moroccan aircraft on social media networks had armed tribesmen and children posing next to wreckage that bore the North African kingdom's national colours of red and green. A corpse also was seen.
The claim by the rebels, also known as Houthis, was made by their mouthpiece television station al-Masar, saying the plane was brought down in the northern province of Saada.
The rebels and allies in Yemen's splintered armed forces routinely fire anti-aircraft guns at warplanes launching strikes in the country since the Saudi-led campaign began March 26.
Morroco's state news agency MAP, citing a military statement, said the pilot of a second jet said he didn't see the pilot of the missing fighter eject. The military said it had launched an investigation into the incident, without elaborating on a cause.
Morocco has six F-16 jets stationed in the United Arab Emirates taking part in the Saudi-led coalition, which includes a group of other Sunni Arab countries.
The West says regional Shiite power Iran backs the Houthis militarily, something both the Islamic Republic and the rebels deny.
If confirmed, the Moroccan F-16 would be the second jet fighter to go down in the conflict. During the early days of the air campaign, a fighter jet crashed in the Arabian Sea off Yemen's southern coast, but the pilot and co-pilot were picked up by a nearby navy vessel. Technical problems were said to have caused the crash.
The raging conflict in Yemen has killed more than 1,400 people - many of them civilians - since March 19, according to the United Nations.
The cease-fire, scheduled to begin Tuesday, would help ease the suffering of civilians in the Arab world's poorest country. Yemenis are suffering from acute shortages of food, fuel and medicine as a result of the bombing campaign as well as a naval, air and land blockade by the coalition.
On Monday, Human Rights Watch said the blockade is keeping out fuel needed for the survival of the Yemeni population, contending that it was a violation of the "laws of war".