The infant mortality rate in Gaza has risen for the first time in more than half a century, a new study by the UN aid agency for Palestinian refugees says.

"The number of babies dying before the age of one has consistently gone down over the last decades in Gaza, from 127 per 1,000 live births in 1960 to 20.2 in 2008. At the last count, in 2013, it had risen to 22.4 per 1,000 live births," said a statement from the UNRWA relief agency, according to AFP.

"Every five years UNRWA conducts a survey of infant mortality across the region, and the 2013 results were released this week," it said, adding that because of the data it would conduct a new Gaza-specific survey this year.

It said that neonatal mortality in Gaza, the number of babies who die before four weeks old, rose from 12 per 1,000 live births in 2008 to 20.3 in 2013.

The statement quoted Akihiro Seita, director of the agency's health programme, as saying that the sudden upswing was unprecedented in the Middle East.