AFP - The UN Children's Fund UNICEF said Friday that 240 villages have reportedly been evacuated and more than 50 schools closed in Saudi Arabia after the conflict in North Yemen spilled over the border.

"UNICEF is deeply concerned about the escalation of the conflict in northern Yemen," said UNICEF regional director for the Middle East Sigrid Kaag.

"Fighting has now spilled over into Saudi Arabia, reportedly causing 240 villages to be evacuated and more than 50 schools to be closed," she added in a statement received in Geneva.

Saudi Arabia said on Tuesday that it would keep up air strikes against Yemeni rebels until they pull back from its border.

Shiite Zaidi rebels said Saudi warplanes had continued to strike them in Yemen, a week after a rebel raid into Saudi territory sparked air and ground bombardment of their positions.

Yemeni forces launched "Operation Scorched Earth" against insurgents in the north of the country on August 11.

UNICEF said the number of displaced to al Mazraq camp in nothern Yemen's Hajjah governorate has more than doubled in four weeks to 15,000, while 28,000 more people who fled fighting were living outside the camp.

"The total number of people displaced by the conflict since 2004 has gone up to more than 175,000, from an estimated 150,000 only a few weeks ago," added Kaag, while malnutrition was reaching "alarming levels" in Yemen.

"UNICEF urges all parties to ensure that children are protected from violence and receive all the assistance they need," said Kaag.