Yemen's foreign minister called Wednesday for a Saudi-led military coalition targeting Shiite rebels in his country to send ground troops.

"Yes I'm calling for this (ground forces) because I think at some stage air strikes will be ineffective," Riyadh Yassin told AFP during an interview in the Saudi capital, where he has taken refuge along with President Abedrabbo Mansour Hadi.

His appeal coincided with warnings from aid groups about a brewing humanitarian crisis and civilian casualties in Yemen, where the coalition began air strikes a week ago.

Yassin said ground forces would cause "less civilian casualties" but added the main reason he proposes a land operation is to enable aid deliveries.

"I am suggesting to start as soon as possible," he added.

"We don't have a safe place from where they can operate," he said of the aid groups.

On Tuesday the Saudi-led coalition's spokesman, Brigadier General Ahmed Assiri, said that "so far there is no need for land intervention" in Yemen but the need might arise "at any time".

A Western diplomatic source on Wednesday said that a land offensive would be "very, very complicated and difficult", partly because it would have to pass mountainous terrain in the country's north, with which the Huthi rebels are highly familiar.

The source ruled out a seaborne landing because the coalition lacks amphibious forces.

But the foreign minister said troops could come in from the south, around the port city of Aden, which would be relatively easy to secure and could become a safe haven for humanitarian operations.

Aid agencies said on Tuesday they could not get assistance into Yemen.

The closure of the country's international airports and restrictions on seaports are hampering delivery, Doctors Without Borders said.

Assiri said all kinds of assistance for Yemen's needy are welcome but the movement of aid needs to be coordinated with the military "to make sure that we don't have any mistakes or any misunderstandings concerning the movement in the ports or airports or through the Saudi border."

Since Friday at least 93 civilians have been killed and 364 wounded in the conflict, the UN human rights office says.

- Iran 'behind all this' -

Amnesty International accused the coalition of "turning a blind eye" to civilian deaths but Assiri said "the coalition takes all care" to avoid hurting the innocent.

"I'm very, very concerned" about the civilian impact, Yassin said, adding that any blame should lie with the Huthis, former president Ali Abdullah Saleh and Iran.

Sunni-majority Saudi Arabia accuses Shiite-dominated Iran of backing the Huthis, who seized power in Yemen's capital Sanaa in February, forcing Hadi to flee to Aden.

He arrived in Riyadh last week after the rebels advanced on Aden, raising Saudi fears they would seize the entire country and take it into Iran's orbit.

"Iran is the one who is behind all this," Yassin said, alleging Tehran wants "to threaten the GCC countries" which include Saudi Arabia and five other Gulf states, while seeking control of the strategic Bab al-Mandab strait and maritime traffic in the area.

The diplomatic source says Saudi Arabia has exaggerated Iranian influence on the militia.

"I think Iran is helping the Huthis but it has limited influence, political influence on the Huthis," the source said.

Tehran has accused Saudi Arabia of an "attack" on Yemen.

Seated in front of a model of traditional Yemeni houses, with a portrait of Hadi above him, Yassin said there can be no negotiations until the "legitimate government" can return to Yemen, Huthis hand over their weapons, and they become a purely political group.

"We are fighting rebels, militia," he said. "They are... like ISIS," he said, referring to the Islamic State jihadist group that has seized swathes of territory in Syria and Iraq.

"Nobody will negotiate with ISIS."

Yassin said the Huthis hold "maybe only 30 percent" of Yemeni territory, concentrated in major cities.

"More than 90 percent of the people of Yemen are with us," he said.