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By Guled Mohamed

MOGADISHU, May 12 (Reuters) - The United Nations' top aid official urged Somali President Abdullahi Yusuf to allow relief supplies to reach his people, during a visit to the Somali capital on Saturday that was disrupted by a deadly blast.

A Somali security source said an explosive device planted in car killed three people near the U.N. compound in Mogadishu shortly after U.N. emergency relief coordinator John Holmes landed, delaying his tour of the shell-shattered city.

The source said the attack targeted a senior intelligence official and not Holmes, the highest ranking U.N. official to visit Somalia since recent clashes killed at least 1,300 people and forced hundreds of thousands to flee their homes.

But a second blast may have been related to the trip, a spokesman for an African Union force said.

"They want to make a point that even when a guest is around we can still set off bombs," the AU's Paddy Ankunda said.

There has been relative calm in the capital since the interim government and its Ethiopian military allies declared victory over insurgents two weeks ago, in a move that has encouraged small numbers of Somalis to return home.

But residents still fear the insurgents -- a mix of Islamist fighters and disgruntled clansmen -- may be regrouping to resist a government they see as propped up by Ethiopia and biased against Mogadishu's dominant Hawiye clan.

The U.N. has accused all sides of breaking humanitarian law by indiscriminately firing on civilian areas in Mogadishu.

"While the fighting was going on we were very, very concerned about the plight of civilians. Clearly, it was not the normal respect for humanitarian law," Holmes told Yusuf.

But Yusuf defended his government's offensive to crush an insurgency that flared after allied Somali-Ethiopian forces ousted rival Islamist leaders from Mogadishu in January.

"Unfortunately these terrorists are conducting guerrilla warfare. Now they have been defeated twice," he said.

"Many of them fled but they left a group of terrorists in the city ... We are very sorry, but we have to pacify this country forever," he added.

FEAR

During the brief meeting, Holmes urged Yusuf to dismantle checkpoints at the city limits to allow food and other relief items to enter Mogadishu as quickly as possible.

It followed complaints by aid workers who accused the authorities of failing to clear food shipments for distribution. The government has promised to clear any obstacles to providing aid to tens of thousands stricken by the fighting.

Holmes also visited the site of the former British embassy, where up to 200 families were living in the shell of the building and in dozens of dome-shaped huts outside it.

Wearing an olive-coloured flak jacket over his pin-striped suit, Holmes crawled into a hut cobbled together with sticks and plastic sheeting to speak to the displaced.

"We are afraid of the fighting, the shelling. We are sometimes attacked in addition to being hungry and thirsty," said Ibrahim Sheikh Mohamed, a former livestock herder.

In another development, Prime Minister Ali Mohamed Gedi sacked one of his deputies, Hussein Mohamed Farah Aideed, and Defence Minister Abdikadir Adan Shire, known as Barre Hiraale.

"I have sacked Hussein Mohamed Aideed for openly opposing the government and Barre Hiraale for failing to carry out his duties," Gedi said in a statement.

Last month, Aideed, a prominent Hawiye, accused Ethiopian troops of "massacring" Somali civilians. Addis Ababa said his comments were propaganda. (Additional reporting from pool reporter Elizabeth A. Kennedy and Ibrahim Mohamed in Mogadishu)

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