The BBC investigation raises questions about Palestinian civilians killed in Gaza. The news broadcaster tried to piece together a fuller picture through claims and videos published by Israel.
“The Israeli military says it has killed more than 10,000 fighters in its air strikes and ground operations, but there are concerns about whether it is able to separate fighters from ordinary civilians,” BBC says.
The toll of at least 30,035 killed provided by the Palestinian health ministry in Gaza has previously been described as trustworthy by the World Health Organization's (WHO) regional emergency director Richard Brennan.
The WHO says the ministry has a "good capacity in data collection" and its previous reporting has been “credible and well developed.”
The Gaza authorities' last demographic breakdown released on 29 February indicated that more than 70 percent of those killed had been women and children.
As the figures suggest that less than 30 percent of the fatalities were men - some of whom are likely to be over fighting age - experts have raised questions about how Israel arrived at its claim of killing 10,000 fighters.
BBC Verify said it “has repeatedly asked the Israeli army for the detail of its methodology for counting Hamas fighter deaths but they have not responded.”
The broadcaster said Israel “issued press statements and social media posts since October,” yet references to numbers of fighters killed in these announcements are “more sporadic and approximate” than the Palestinian health ministry's regular updates on fatalities.
On 29 December, an Israeli Army Spokesman Major Doron Spielman told Sky News Australia that 8,000 Hamas fighters had been killed, saying the figure was based on intelligence, interrogations and examination of satellite photographs.
In mid-January, Prime Minister Benjamin Netanyahu claimed Israel had "destroyed" two-thirds of Hamas fighting regiments in Gaza.
On 19 February, the Times of Israel reported that the army had killed 12,000 fighters.
Meanwhile, the occupation army, in two separate responses to BBC, said the figure is "approximately 10,000" and "more than 10,000", while the Israeli embassy said they think the total number of fighters killed is "between 10,000 and 12,000".
However, they admitted that it was hard to distinguish between civilians and combatants.
BBC Verify also reviewed all 280 videos posted on the Israeli army YouTube channel from 7 October up to 27 February and found that “very few contained visual evidence of fighters being killed.”
Of these, just one - posted on 14 December - purports to show dead bodies of fighters. A handful of other videos appear to show fighters being shot at.
BBC also attempted to count the number of individual claims of Hamas fighters killed on the Israeli army's official Telegram channel. “We found 160 posts claiming to have killed a specific number of fighters, for a total of 714 fatalities.”
But there were also 247 references which used terms such as "several", "dozens" or "hundreds" killed, making a meaningful overall tally impossible.
Some experts are concerned that Israel might be counting some non-combatants as fighters, BBC reported.
The fatality data for the current war from the Palestinian health ministry in Gaza shows a sharp increase in the proportion of women and children among the dead compared with previous wars.
This "indicates a much higher civilian death rate," according to Rachel Taylor, the executive director of the Every Casualty Counts organisation, a UK-based organisation that aims to record victims of violent conflicts.
Nearly half of Gaza's population is under 18, and about 44 percent of the fatalities of war are also children, according to the Gaza authorities' demographic data released on 29 February.
Taylor said the fact that the deaths closely track the demographics of the general population "indicates indiscriminate killing.”
"In contrast, in 2014 there was a fairly high percentage of 'fighting age' men among the dead, but this is much less evident today," she said.
Some experts also told the BBC that the real scale of those killed by the Israeli attacks is likely to be significantly higher as many hospitals, where deaths are usually recorded, are no longer operating.
These figures also only include deaths from military attacks, according to the Palestinian health ministry's spokesman, and no deaths due to starvation or disease, which are increasingly concerning international aid organisations.
B'tselem, a Jerusalem-based human rights organisation, said the current war is far deadlier than previous conflicts between Israel and Gaza.
Spokesperson Dror Sadot said: "These are numbers that we never saw in previous wars and strikes in Gaza or the other territories."
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