Several metres deep. In the north of the territory, the un says a convoy of its staff carrying out polio vaccinations was held at gunpoint for eight hours by the israeli army on monday. The staff have now been released, but the un says it s not sure whether it can continue the vaccination campaign as planned. Meanwhile, syria says at least 18 people have been killed and dozens injured in a series of israeli air strikes. Syrian state media says multiple sites were targeted including scientific research centres. Monitoring organisations say that one of the sites, in the city of masyaf, was housing pro iranian weapons experts. Iran rejected reports that iranian sites were hit. Israel says it will not comment on reports of the strikes. Israel has previously acknowledged carrying out hundreds of strikes in recent years on targets in syria that it says are linked to iran. Joining me is frank lowenstein, who served as united states special envoy for middle east peace under president barack ob