UNITED NATIONS -- Smugglers have thrown 280 migrants into the sea off the coast of Yemen in the last two days, causing more than 50 to drown and leaving over 30 missing, the U.N. migration agency said Thursday.

U.N. spokesman Stephane Dujarric said the migrants who were forced from boats in two separate "deeply troubling" incidents were hoping to reach countries in the Gulf via war-torn Yemen.

The International Organization for Migration said Wednesday that up to 50 migrants from Ethiopia and Somalia were "deliberately drowned" by a smuggler off Yemen when 120 migrants were forced into the water. The U.N. agency said 160 Ethiopian migrants were violently forced into the Arabian Sea on Thursday.

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The IOM said in a statement late Thursday that its staff found six bodies on the beach -- two male and four female -- and 13 people are still missing. It said 84 migrants left the beach before IOM staff arrived while it provided emergency medical assistance as well as food and water to 57 surviving migrants.

Dujarric said the situation for migrants trying to cross the Mediterranean Sea and the Sahara desert are "just as heartbreaking" as the tragedy unfolding off Yemen.

He said 2,405 people have died or disappeared during their attempts to cross the Mediterranean and more than 265 people have died or were missing while traveling across the Sahara trying to reach the sea.

U.N. Secretary-General Antonio Guterres "is heartbroken by this continuing tragedy," Dujarric said.

"This is why he continues to stress that the international community must give priority to preventing and resolving a variety of situations which both generate mass movement and expose those already on the move to significant danger," the U.N. spokesman said.

"We must also increase legal pathways for regular migration and offer credible alternative to these dangerous crossings for people in need of international protection," Dujarric said.

The narrow waters between the Horn of Africa and Yemen have been a popular migration route despite Yemen's conflict. Migrants, most of them Ethiopians, try to make their way to oil-rich Gulf countries in hopes of finding jobs.

Laurent de Boeck, the IOM's chief of mission in Yemen, told The Associated Press on Thursday that some of the migrants trying to reach Yemen "are not aware at all that there is a war. Sometimes they don't even believe us when we explain it to them."

Just by making land they feel "they are halfway to wealthy," he said.

In the first drownings on Wednesday, a smuggler forced more than 120 migrants into the sea as they approached Yemen's coast, the IOM said. Its staffers found the shallow graves of 29 migrants on a beach in Shabwa during a routine patrol. At least 22 migrants remained missing.

The passengers' average age was around 16, the IOM said.

IOM staff assist Somali and Ethiopian migrants who were forced into the sea by smugglers. U.N. Migration Agency

"The survivors told our colleagues on the beach that the smuggler pushed them to the sea when he saw some 'authority types' near the coast," de Boeck said earlier. "They also told us that the smuggler has already returned to Somalia to continue his business and pick up more migrants to bring to Yemen on the same route."

De Boeck called the suffering of migrants on the route enormous, especially during the current windy season on the Indian Ocean.

"Too many young people pay smugglers with the false hope of a better future," he said.

The IOM says about 55,000 migrants have left Horn of Africa nations for Yemen since January, most from Somalia and Ethiopia fleeing drought and unrest at home. Many leave from points in Djibouti, with some departing from Somalia. A third of them are estimated to be women.

"Some are coming for the third time. They didn't succeed, they went back home, but the parents didn't agree with the fact that they didn't succeed so they send them back. And they have no choice," de Boeck told the AP. "They are between 12 and 25 years old."

Migrants travelling from Djibouti pay about $150, while migrants travelling from northern Somalia pay between $200 and $250 because the route to Yemen is longer.

De Boeck expressed regret that the European Union is more focused on Mediterranean routes where smugglers have also cast migrants trying to reach Europe adrift.

"They have forgotten us a little bit," de Boeck said.

In Ethiopia, people expressed outrage on social media over the drownings.

"This is an unprecedented level of cruelty," wrote one Facebook user, Behailu Talegeta.

Despite the fighting in Yemen, African migrants continue to arrive in the country where there is no central authority to prevent them from traveling onward. The migrants are vulnerable to abuse by armed trafficking rings, many of them believed to be connected to the armed groups involved in the war.

Yemen's conflict itself is a deadly risk. In March, Somalia's government blamed the Saudi-led coalition fighting in Yemen for an attack on a boat that killed at least 42 Somali refugees off Yemen's coast.

More than 111,500 migrants landed on Yemen's shores last year, up from around 100,000 the year before, according to the Regional Mixed Migration Secretariat, a grouping of international agencies that monitors migration in the area.