Tehran: Iranian President Hassan Rouhani says, a Saudi-led offensive in Yemen was prompted by the kingdom's failures elsewhere, causing what he called a "mental imbalance".

Speaking to reporters today before heading to Indonesia, Rouhani mocked Saudi Arabia by calling it a country with dashed dreams in Iraq, Syria and Lebanon.

"All the failures have accumulated and caused mental and emotional imbalance for that country," Rouhani said.

Iran has long accused Saudi Arabia of supporting militants, including the self-styled Islamic State (IS) group in Syria and Iraq. Meanwhile, Saudis accuse Iran of supporting Yemen's Shia Houthi rebels who overran the capital and later forced the country's Western-backed president into exile.

Tehran and the rebels deny any military links, though the Islamic Republic has provided political and humanitarian support to the group.

Clashes between rebels and pro-government forces and Saudi-led air strikes killed at least 85 people in Yemen last week.

The United Nations says hundreds of people have died and thousands of families have fled their homes since the coalition air war began on March 26 at the request of embattled President Abedrabbo Mansour Hadi.

The UN agency for refugees says that up to 150,000 people have been displaced over the past three weeks, while more than 300,000 had already fled their homes because of unrest in past years.

Last month, the Kingdom and its allies launched air strikes in Yemen against Houthi fighters, who have tightened their grip in southern city of Aden where the country's president had taken refuge, the Saudi envoy to Washington had said.

The kingdom's ambassador to the United States announced from Washington last month that a coalition of 10 countries, including the five Gulf monarchies, had been set up to protect the Yemeni government.