Yemen's government is to request membership of the Gulf Cooperation Council (GCC), the powerful grouping of Sunni Arab Gulf monarchies, a spokesman for the country's president, has said.

Rajeh Badi told the Reuters news agency on Wednesday that the country would "present a plan in Saudi Arabia next month that will prepare Yemen to be included in the GCC".

The GCC comprises Saudi Arabia, the United Arab Emirates (UAE), Oman, Bahrain, Kuwait and Qatar - countries that operate with close political, economic and military ties.

A coalition, which includes five out of six GCC countries, has been bombing Houthi targets in Yemen for weeks, but has failed to reverse the group's dominance on battlefronts across the country.

The Houthis, who belong to the Zaydi sect of Shia Islam, continued their advance on the southern coastal city of Aden on Wednesday, capturing parts of an upscale neighborhood.

Sources told Al Jazeera that many residents fled after dozens of homes and shops were shelled by Houthi tanks in the busy district of Khormaksar.

At least 12 civilians were killed by Houthi tanks and sniper fire overnight, as the rebel group clashed with local fighters.

Several air strikes reportedly hit Houthi positions in Khormaksar, however the source said the group's tanks, stationed in residential areas, remained intact.

The source added that the Houthis were trying to advance on the Al-Tawahi neighbourhood, in the west of the city, where the presidential palace, security headquarters and TV stations are located.

"The world, the coalition and the United Nations need to step in urgently to save our neighbourhood, which has truly become a disaster area after this indiscriminate shelling," Ali Mohammed Yahyam, a resident said.

On Monday, the Houthis stormed the Republican Hospital in Aden, firing heavily and forcing medical staff, including Red Cross doctors, to flee while detaining some of the wounded receiving treatment there.

Aden has seen fierce fighting for weeks, as the Houthis and troops loyal to former President Ali Abdullah Saleh try to wrest the city from local fighters and supporters of President Abd-Rabbu Mansour Hadi who has fled to Saudi Arabia.

About 200km to the north, coalition aircraft dropped weapons for tribal fighters in the city of Taiz, where they have been battling the Houthis with heavy artillery in city streets for days.

Airstrikes continued throughout the country on Wednesday, hitting targets in Aden, Hajja, Taiz, Ibb, al-Bayda and the Houthis stronghold of Saada.

Saudi-trained fighters

Despite weeks of bombing, the Houthis have retained their dominant position across much of Yemen, and no visible progress has been made towards peace talks.

Earlier this week, 300 tribal fighters were trained in Saudi Arabia before being deployed to their home area in the Sirwah district of central Marib province to fight the Houthis, a Yemeni official source told Reuters.

The Houthis, who seized control of the capital Sanaa in September after demanding a more inclusive government, have rattled Saudi Arabia and its allies, who fear what they see as expanding Iranian influence in the region. Tehran denies supporting the Houthis.

Since late March, at least 1,080 people have been killed, according to the UN, with bodies often crushed under bombed homes.

According to the UN, 12 million people are "food insecure" or going hungry, a 13 percent increase since the conflict started, as a blockade has choked off imports of food and medicines, while combat has interrupted fuel supplies to the country's 25 million people.