"We urge the international community to quickly intervene by land forces to save Yemen," Yemeni Ambassador Khaled Alyemany said in a letter to the United Nations Security Council.
The request came on the same day shells struck boats trying to flee the southern Yemeni city of Aden, killing more than 50 people, Alyemany said. He blamed Houthi militias for the strikes.
The letter accused rebels and forces loyal to former Yemeni President Ali Abdullah Saleh of "targeting anything that moves in the city of Aden, preventing medical teams and volunteers from reaching the injured and killing humanitarian agents."
Heavy clashes also erupted Wednesday in Aden's Tawahi port district, according to two Yemeni officials.
Forces supporting President Abdu Rabu Mansour Hadi -- backed by airstrikes -- battled Houthi fighters, who took control of the port, the officials said.
The clashes are the latest in Yemen's months of violence, which exploded before Hadi's ouster from Yemen by the Iranian-backed Houthis.
He and forces loyal to him haven't given up though, battling the Houthis with the help of Saudi Arabian-led airstrikes. The Saudis say they want to restore what they call Yemen's legitimate government led by Hadi.
The fighting has exacerbated the difficult humanitarian situation, spurring hundreds of civilians to flee Aden and other cities across the nation.
The United Nations estimates
300,000 people have been displaced within in Yemen since March, with 12 million in need of food.
Earlier this week, U.N. humanitarian coordinator Johannes Van Der Klaauw issued a statement saying the violence, including airstrikes targeting the runways at the international airport in the capital of Sanaa, have hampered efforts to deliver aid.
"Without access to the airports, aid agencies are unable to bring in staff, vital supplies of medicines and other critical life-saving assistance, or undertake medical evacuations of their personnel," Van Der Klaauw said. "Emergency relief and medical teams from abroad are likewise unable to fly in to scale up the humanitarian operation to address the needs of increasingly vulnerable Yemenis."