A man stands near cars damaged by an air strike on a nearby Scud missile base in Yemen's capital Sanaa April 20, 2015. [Photo/Agencies]

The exiled Yemeni government said in the Saudi capital of Riyadh that negotiations will not be held until the Houthi fighters are disarmed and retreat from areas they seized since September 2014.

However, the leader of the Houthi group, Abdul Malik al-Houthi, condemned the Saudi-led military operations on Sunday and vowed to take tougher actions to confront the coalition forces and Sunni tribal fighters.

In his first televised speech since the airstrikes began late March, al-Houthi accused Riyadh of interfering in Yemen's domestic affairs, saying that "we can decide our politics, form our government."

"We took government institutions to protect those from al-Qaida," he said. "They asked us to withdraw from ministries and from southern provinces in order to let al-Qaida to seize them."

"This will not happen," al-Houthi said. "The Yemeni people will never surrender and we are entitled to respond to this aggression by all open options."

Aid agencies, including the Red Cross, the World Health Organization and Doctors Without Borders, have started to distribute medicine in the country after their shipments arrived in Sanaa international airport and the southern Aden port last week.

However, they have difficulty entering into the hot spots, especially Aden city and Shabwa province, where deadly fighting persisted between Houthi fighters and pro-Hadi tribal militias.