(U.S. condemns killing of two journalists, paragraphs 8-11)

MOGADISHU, Aug 13 (Reuters) - Explosions in Somalia's capital on Monday killed four police officers and one civilian in the latest attacks by suspected Islamist rebels, police said.

The attacks come in the wake of the killings of two top Somali journalists over the weekend and intensified assaults on Ethiopian-backed Somali troops by suspected insurgents.

"A remote controlled landmine exploded near one of our vehicles carrying policemen. Four police officers died from the blast. This is definitely caused by the insurgents," police commander Abdullahi Hassan Barise told Reuters.

Three policemen were wounded, he said adding that there could have been civilian casualties as the explosion had occurred in a busy area.

In a separate explosion in south Mogadishu, one person died and three were wounded when a landmine targeting a police vehicle exploded and hit a bus instead, witnesses said.

"The police escaped unhurt. We were very fortunate we were not caught in the blast," resident Sheikh Salab said.

Mogadishu, one of the world's most violent cities, has been rocked by violence since January when the interim government and Ethiopian troops drove out Islamists who had ruled much of southern Somalia for six months last year.

In Washington, the U.S. State Department issued a statement condemning the killing on Saturday of two respected Somali journalists who worked at HornAfrik, an independent FM radio station, in Mogadishu.

Popular talk show host Mahad Ahmed Elmi was shot four times in the head at close range as he neared the door of his office and later the founder and co-owner of HornAfrik -- Ali Iman Sharmarke -- died when his four-wheel drive hit an explosive device in the road on his way back from Elmi's funeral.

"These senseless murders highlight the determination of violent extremists to undermine the political process by threatening the media and the voices of those who seek reconciliation in Somalia," said State Department spokesman Sean McCormack.

"We urge civil society, clan and religious leaders, to honor Sharmarke and Elmi by renewing their commitment to peace, reconciliation, and a stable political future for Somalia," he added. (Additional reporting by Arshad Mohammed in Washington)

AlertNet news is provided by