Explosion outside Aden govt building kills four

An explosive device detonated next to the governor's office in the southern Yemeni city of Aden on Thursday, a local official and witnesses said, killing four people and wounding 11, several of them critically.

The blast underscores instability in Yemen's second largest city a month after fighters loyal to the country's government in exile, backed by arms and hundreds of air strikes from rich Gulf Arab states, seized it from Iran-allied Houthi forces.

The governor was inside but unhurt, an official said.

Meanwhile, heavy Arab air strikes hit targets throughout northern Yemen on Thursday, local officials said, as the frontlines approach Houthi strongholds there.

The attacks hit five provinces controlled by the Houthis and the military airport in the capital Sanaa amid rapid ground advances by the Arab-backed Yemeni fighters.

The Saudi-led alliance began the air strikes in late March as the Shi'ite Muslim militia from Yemen's north entered Aden, in a civil war that has killed over 4,300 people and left diplomats and air groups appealing for a ceasefire to spare civilians and alleviate a mounting humanitarian disaster.

"No nation, no society, can afford to lose its children to conflict - whether from direct attacks, from malnutrition, from disease, from lack of education, or from the traumas of the horrors they witness," U.N. agency UNICEF said in a statement, noting that around eight children have been killed or wounded in the war every day.

Sunni Arab countries and Yemen's Saudi-based government see the Houthis as a proxy of Shi'ite Iran bent on extending the Islamic Republic's influence in the Arab world.

The Houthis and Iran deny this, saying their armed spread is a revolution against officials and Arab countries aligned with Sunni militants like al Qaeda and subservient to the West.

Southern Yemeni militias and loyalist army units have scored major gains against the Houthis in the last month and may soon advance toward their stronghold around Sanaa.

But as a political accord remains elusive, suffering and hunger continue to spread especially after the coalition bombing of northern Yemen's main entrepot in the Red Sea port of Hodaida this week.

Ertharin Cousin, the head of the U.N.'s World Food Program, warned after a three-day visit to the country that the violence and near-blockade by Arab forces may push already widespread hunger out of control.

"Ten of the 22 governorates in Yemen in July were already at emergency levels. That's one step away from famine."