Palestinian health authorities say Israel's ground and air campaign in Gaza has killed more than 35,000 people, mostly civilians, and driven most of the enclave's 2.3 million people from their homes.

The war began on Oct 7 when Hamas militants stormed across the border into Israeli communities. Israel says the militants killed more than 1,200 people, mostly civilians, and dragged 253 into captivity in Gaza.

This explainer examines how the Palestinian death toll is calculated, how reliable it is, the breakdown of civilians and fighters killed and what each side says.

HOW DO GAZA HEALTH AUTHORITIES CALCULATE THE DEATH TOLL?

In the first months of the war, death tolls were calculated entirely from counting bodies that arrived in hospitals and data included names and identity numbers for most of those killed.

As the conflict ground on, and fewer hospitals and morgues continued to operate, the authorities adopted other methods too.

A May 7 Health Ministry report gave an overall toll of 34,844. It said 21,058 of those deaths were counted from bodies that hospitals reported arriving at morgues. Another 3,715 were deaths reported online by family members who had to input information including identity numbers.

It listed the remaining 10,071 deaths as having "incomplete data".Omar Hussein Ali, head of the ministry's emergency operations centre in the Israeli-occupied West Bank, said these were bodies that had arrived at hospitals or medical centres without personal data such as identity numbers or full names.

IS THE GAZA DEATH TOLL COMPREHENSIVE?

The numbers "do not necessarily reflect all victims due to the fact that many victims are still missing under the rubble", the Palestinian Health Ministry says. In May it estimated that some 10,000 bodies were uncounted in this way.

The U.N. human rights office and the Humanitarian Research Lab at the Yale School of Public Health have also said during the conflict that the true figures are likely higher than those published.

HOW CREDIBLE IS THE GAZA DEATH TOLL?

Pre-war Gaza had robust population statistics and better health information systems than in most Middle East countries, public health experts told said.

A spokesperson for the World Health Organisation said the ministry has "good capacity in data collection/analysis and its previous reporting has been considered credible".

The United Nations regularly cites the ministry's death toll figures, while naming the ministry as the source.

Early in the conflict, after US President Joe Biden cast doubt on casualty figures, the health ministry published a detailed list of the 7,028 deaths that had been registered by that point.

Academics looking at details of listed casualties said in a peer-reviewed article in the Lancet medical journal in November that it was implausible that the patterns shown in the list could be the result of fabrication.

However, there are specific questions over the inclusion of 471 people said to have been killed in an Oct. 17 blast at al-Ahli al-Arab hospital in Gaza City. An unclassified US intelligence report estimated that death toll "at the low end of the 100 to 300 spectrum".

DOES HAMAS CONTROL THE FIGURES?

While Hamas has run Gaza since 2007, the enclave's Health Ministry also answers to the overall Palestinian Authority ministry in Ramallah in the West Bank.

Gaza's Hamas-run government has paid the salaries of all those hired in public departments since 2007, including in the Health Ministry. The Palestinian Authority still pays the salaries of those hired before then.

The extent of Hamas control in Gaza now is difficult to assess with Israeli forces occupying most of the territory, including around locations of major hospitals that provide casualty figures, and with fighting ongoing.

WHAT DOES ISRAEL SAY?

Israeli officials have said the figures are suspect because of Hamas' control over government in Gaza. Foreign Ministry spokesperson Oren Mamorstein said the numbers were manipulated and "do not reflect the reality on the ground".

However, Israel's military has also accepted in briefings that the overall Gaza casualty numbers are broadly reliable.

Last week Israeli Prime Minister Benjamin Netanyahu said 14,000 Hamas fighters and 16,000 Palestinian civilians had been killed in the war.

HOW MANY CIVILIANS HAVE BEEN KILLED?

The Health Ministry figures do not differentiate between civilians and Hamas combatants, who do not wear formal uniform or carry separate identification.

Israel periodically provides estimates of how many Hamas fighters it believes have been killed. The most recent was Netanyahu's estimate of 14,000.

Israeli security officials say such estimates are reached through a combination of counting bodies on the battlefield, intercepts of Hamas communications and intelligence assessments of personnel in targets that were destroyed.

Hamas has said Israeli estimates for its losses are exaggerated but has not said how many of its fighters have been killed.

The Palestinian Health Ministry says more than 70% of the dead are women and children under 18. For most of the conflict its figures showed children as representing slightly over 40% of all those killed.

However, conditions in hospitals compiling figures have worsened amid the fighting and many of those killed may not be identifiable due to their injuries.

In May the ministry updated its breakdown of the fatalities to be based only on the 24,686 bodies it said had been fully identified, and not on the more-than 10,000 bodies it said have not yet been identified.

When it made this change, the numbers appeared significantly less, prompting Israel to raise further questions over the figures.