Experts discuss how long rebuilding Gaza's $18.5 billion of damaged infrastructure could take after 15 months of conflict.

Israel on Monday began allowing Palestinians to return to the heavily destroyed north of the Gaza Strip for the first time since the early weeks of the 15-month war with Hamas, in accordance with a fragile ceasefire.

The opening was delayed for two days over a dispute between Hamas and Israel, which said the militant group had changed the order of the hostages it released in exchange for hundreds of Palestinian prisoners.