Geneva, Nov 8 (IANS): A week after the Middle East declared a polio emergency, a large-scale immunisation response in the region is under way.

The move aims to vaccinate over 20 million children in seven countries and territories, Xinhua cited the World Health Organization (WHO) as saying Friday.

The seven countries and territories in the consolidated emergency response to the polio outbreak include Egypt, Iraq, Jordan, Lebanon, the West Bank and Gaza, Syria and Turkey.

It said the immunisation campaign inside Syria, which is targeting 1.6 million children to prevent transmission of polio and other preventable diseases, has vaccinated more than 650,000 children, including 116,000 in Deir al-Zour province where the polio outbreak was confirmed a week ago.

The first polio outbreak in Syria since 1999, it has so far left 10 children paralysed, and poses a risk of paralysis to hundreds of thousands of children across the region.

Preliminary evidence indicates that the polio virus is of Pakistani origin and is similar to the strain detected in Egypt, Israel, the West Bank and Gaza Strip over the last 12 months, according to the WHO.

The UN Children's Fund (Unicef) said it has procured 1.35 billion doses of oral polio vaccine (OPV) to date in 2013 and by the end of the year will have procured up to 1.7 billion doses to meet increased demand.

The new outbreak in Syria is adding further pressure to the supply of OPV but WHO, UNICEF and manufacturers are working to secure sufficient quantities to reach all children, it said.

The largest ever consolidated immunisation response to polio virus circulation in the region includes plans for a six-month sustained effort of intense immunisation activity.

UN agencies also have suggested strengthening of disease surveillance until the global eradication of polio, and to find cases which may have been missed in an environment which was until recently polio-free.