SANAA, March 26 -- Warplanes raided military camps belonging to the Shiite Houthi group in Yemen's capital Sanaa on Thursday, killing four civilians, a defense ministry official told Xinhua.

The warplanes struck the al-Dailamy air force base in northern Sanaa and destroyed the runway, which is adjacent to the civil airport, the official said on condition of anonymity.

The strikes also targeted weapons depots at a missile base in the southern part of Sanaa, which is controlled by the army loyal to former President Ali Abdullah Saleh.

The official said four civilians were killed in the air strike on the air force base. However, the Houthi-run al-Maseera TV reported that dozens of people were killed overnight, without giving further details.

Intensified sounds of anti-aircraft artillery could be heard across the capital city. Residents near the airport said they heard explosions and saw fires in different places in the military base of al-Dailamy.

They said Houthi fighters deployed several anti-aircraft guns on main streets in Sanaa.

Mohammed al-Boukhaiti, a member of the Houthi political bureau, told Xinhua that "Saudi aggression is a declaration of war against the Yemeni people and we will fight them."

He said Saudi Arabia began the war which would plunged the whole region into an all-out war and the Houthi group was obliged to deal with this "aggression."

The General People's Congress, the former ruling party led by Saleh, said in a statement posted on its website that "the Saudi air aggression violates the Charter of the United Nations and the agreement signed by the Saudi and Yemeni governments."

It said the Saudi airstrikes targeted the Sanaa airport and al-Dailami air force base, causing huge explosions that shocked the capital Sanaa as anti-aircraft artillery responded to confront the Saudi aggression.

Yemeni President Abd-Rabbu Mansour Hadi and its main ally Saudi Arabia have accused Saleh of supporting the Houthi group to overrun the country.

Najeeb Ghalab, a politics professor at Sanaa University, said "the Arab intervention reflected united Arab position toward the situation in Yemen and that leaves no room for any faction to maneuver or risk reckless moves."

However, observers said there is little chance that the air raid could prevent the Houthi group from seizing the southern port city of Aden, as their fighters already took over the Aden international airport and most of pro-Hadi tribal militia started to retreat from the city to neighboring Abyan province.

Intensified gunfire could be heard on the outskirts of Aden on Thursday morning, which the president proclaimed as the temporary capital last week. Capital Sanaa has now been under control of the Houthi group for almost half a year.

In the port city, all foreign diplomatic missions were suspended. The Aden international airport was shut down because all of its staff have left for fears, but diplomats of the Gulf Arab nations have already flown out of the country.

A source inside the presidential palace said Friday that Hadi is still in Aden to command his forces to battle against the Houthi group.

A senior Houthi member told Xinhua that the group has arrested Defense Minister Major General Mahmoud al-Subaihi in Lahj province who has been commanding most of the pro-Hadi army to battle the Houthis.

When al-Subaihi was escorted to Sanaa, most of the army troops have surrendered to the Houthi group, leaving a small number of soldiers and tribal militia to defend Hadi in Aden.

However, Fathi Abu Alnasr, an analyst based in Sanaa, argued that the Arab military action is helpful for now while Houthis and pro-Saleh forces are fighting in many parts. However, he did not exclude bad consequences that could happen.

"The intervention is destroying Houthi and Saleh forces but in principle it remains a rejected invasion of Yemen," he said.