Sana'a, Yemen - Yemeni army forces launched an all-out onslaught on Shiite rebels in the north-western province of Saada on Tuesday, official and tribal and sources said.

Tribal sources told the German Press Agency dpa that the army began aerial, artillery and missile strikes on the strategic heights of Matra and Dhahian, the two main strongholds of the rebels on the border with Saudi Arabia.

The country's Supreme Security Committee said in a statement that the assault was "the last option after the rebels rejected to respond to the call of peace made by the government."

The committee said the government ordered the army to launch the attack "to protect the citizens in line with its constitutional responsibility."

It vowed to "strike them (the rebels) with an iron fist until they give themselves up to justice."

The media office of the rebel leader Abdul-Malik al-Houthi said in a statement that fighter jets bombarded the Matra twon, where the group is headquartered.

"This is the beginning of the sixth aggression (war) against us," said the statement, e-mailed to the German Press Agency dpa.

"We are ready for them (the troops), and their losses this time round will be much higher than in the previous wars," the statement said.

Tensions have been rising in recent months between the rebels, known as Houthis, and the army in Saada since last July when Yemeni President Ali Abdullah Saleh declared the conflict over.

Five waves of fierce battles between the rebels and army forces have left hundreds of soldiers and insurgents dead since the fighting erupted in 2004.

Authorities have accused the rebels of trying to reinstall the rule of imams, which was toppled by a republican revolution in northern Yemen in 1962.

The Houthis belong to the Zaidi sect, an offshoot of Shiite Islam.(dpa)