Fierce fighting has been reported in Yemen's coastal city of Aden as Houthi rebels continued their push south despite a fifth night of Saudi-led airstrikes against the group's positions.

Clashes were reported in the Dar Saad district of Aden on Sunday as fighters loyal to President Abd-Rabbu Mansour Hadi battled Houthis trying to push their way to the city's northern gate.

Hadi loyalists told Al Jazeera they had recaptured the airport, which has changed hands several times in recent days, as a gun battle raged in Aden's central Crater district.

Nearly 100 people are reported to have been killed in the violence in Aden in recent days.

Heavy fighting was also reported in Shabwa province, with local tribes in Beihan telling Al Jazeera that at least 40 Houthi fighters were killed in battles there.

The clashes came as Nabil el-Araby, the head of the Arab League, said Saudi-led airstrikes would continue until the Houthis layed down their weapons and withdrew.

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"Yemen was on the verge of collapse which prompted a reaction from Arab states and the international community," el-Araby said.

"The [airstrikes] came after all other means to achieve a peaceful solution ... were exhausted. The [strikes] will continue until the Houthis hand over their weapons."

Meanwhile, Adel al-Jubeir, Saudi Arabia's ambassador to the US, said the kingdom was keeping its options open over whether to send ground troops to Yemen.

"I don't know that anyone wants to go into Yemen but we don't rule anything out," Jubeir was quoted by the Reuters news agency as saying. "Right now the objective is being achieved through an air campaign,"

In some of the latest airstrikes carried out by the Saudi-led coalition, raids targeted the Houthis' main stronghold of Saada in the north and also hit ammunition depots and airports.

"The coalition has been targeting the air defence capabilities of the Houthis, including Surface-to-air missiles, artillery, and anti-aircraft batteries," said Brigadier General Ahmed Asiri, the spokesman for the Arab coalition bombing Houthi targets on Sunday. He also accused the Houthis of amassing a "huge stockpile of weapons in all cities of the republic."

However, Asiri said operations over Hodeida were halted for two hours to allow the evacuation of 500 Pakistani nationals.

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In the northern city of Saada, a Houthi stronghold near the Saudi border, raids hit bases under the control of the group and their ally, former President Ali Abdullah Saleh, who still controls most army units.

Saleh stood down after a 2011 uprising but still wields wide influence in Yemen.

He appealed on Saturday to Arab leaders meeting in Egypt to halt their offensive and resume talks on political transition in Yemen, promising that neither he nor his relatives would seek the presidency.

Riyadh Yasin, Hadi's foreign minister, dismissed his comments as "the talk of losers".

Meanwhile, Saudi-owned television channel Al-Arabiya broadcast a detailed account of a proposal by Saleh's son Ahmed to the Saudi leadership to head off military intervention.

Al-Arabiya said Prince Mohammad rejected Ahmed's proposal where he said he would break with the Houthis.

"There must be a return to legitimacy in the form of President Abd-Rabbu Mansour Hadi to lead Yemen from the capital Sanaa," it quoted him as saying.