Israeli forces have killed at least 20 journalists since 2001 in cases showing a pattern of "inadequate responses that evade accountability", a watchdog says.

A report by the Committee to Protect Journalists (CPJ) describes routine obfuscation and failure to properly investigate by the Israeli military.

It says the journalists' deaths and insufficient responses constitute a "grave threat to press freedom".

It comes ahead of the first anniversary of the killing of Shireen Abu Aqla.

The Palestinian-American Al Jazeera correspondent was shot dead during an Israeli military raid in the occupied West Bank on 11 May 2022.

The vast majority of the journalists killed in the last two decades were Palestinian.

The Israel Defense Forces (IDF) said in response to the report that its forces did not target journalists, who through their work were often present near "violent riots" or "shooting attacks" towards Israeli forces or civilians

"During intense combat situations, the IDF only strikes at military targets and takes all possible precautions in order to reduce harm to civilians during its operational activities," it added.

The IDF also said that it "regularly examines and investigates its actions through independent and in-depth inspection and investigation mechanisms".

The CPJ report details around two thirds of what it says are at least 20 cases of correspondents, camera operators, producers or other media workers killed by Israeli military fire since 2001.

In the case of Abu Aqla, who was shot in the head during an IDF raid in Jenin refugee camp, the report notes that "to date no-one has been held accountable", adding that her killing "was not an isolated event".

Since 2001, 18 Palestinians and two European foreign journalists - one Italian and one British - have been killed by Israeli military fire and no-one has ever been charged or held to account, the report says.

"The degree to which Israel claims to investigate journalist killings depends largely on external pressure," says Sherif Mansour, CPJ's Middle East co-ordinator.

"There are cursory probes into the deaths of journalists with foreign passports, but that is rarely the case for slain Palestinian reporters. Ultimately, none has seen any semblance of justice," he adds.

Israel maintains it has robust processes for investigating the actions of its forces.

Since 2014, it has operated a system of "fact finding assessments" into civilian deaths, which can progress to a criminal investigation by the Military Advocate General.

But in the nine years since the system has been in place, no case involving the death of a journalist has reached criminal proceedings and no soldier has been held accountable, the report says.

Among other cases highlighted in the report are those of Palestinian video journalist Yaser Murtaja and freelance reporter Ahmed Abu Hussein, both of whom were shot dead by Israeli snipers in separate incidents while they covered Palestinian protests at the Gaza perimeter fence in 2018.

The Palestinian journalists' union at the time accused Israel of "deliberately" targeting them.

The Israeli military told the report that the two journalists were "allegedly present at the scene of violent riots" and "no suspicion was found which would justify the opening of a criminal investigation" into the soldiers.

In the case of Murtaja, the CPJ report says Israel's then-defence minister Avigdor Liberman spent weeks "trying to discredit the journalist" by saying he was a senior member of the armed wing of the Palestinian militant group Hamas, without presenting any evidence.

It later emerged that the journalist had been vetted by the US to receive international development funding for his production company.

In the case of Abu Hussein, human rights campaigners filed a request for the military to investigate his death.

But the CPJ report says the IDF closed the case two years later without interviewing any witnesses, saying there was no criminal intent by the soldiers.

Abu Hussein's mother Raja said the military never contacted her about its probe. "The typical answer the Israeli army gives when it kills civilians is that the army did nothing wrong," she told the report's authors.

"I wish I could meet the guy who killed my son... I would ask him, 'Why, why did you target my son?' I think he won't have an answer. He is a sniper, he kills," she said.

Under international law, the use of firearms by security forces against civilians is defined as a measure of last resort, and can only take place to stop an "imminent threat of death or serious injury".?

The IDF routinely responds to cases of civilians hit, including journalists, by saying that soldiers use lethal force to stop rioting or amid fire aimed at them by Palestinian militants.

The CPJ report describes a "pattern" of evading accountability by the IDF and other officials including discounting evidence and witness claims, pushing false narratives, accusing journalists of terrorism and opening probes only under international pressure.

The IDF has previously said it was "highly probable" its soldiers fired the shot that killed Shireen Abu Aqla, but described it as "unintentional" - a claim disputed by her family.

The IDF said its enforcement policy regarding deaths during operational activity has been approved by several Supreme Court rulings.

Shlomo Zipori, a former chief defence attorney in the Military Advocate General's unit, told the report that soldiers may overthink their moves in the field if they fear being tried.

"I represented a soldier who was still serving in the army while under criminal investigation for killing a Palestinian and injuring another," he said.

"Someone threw a Molotov cocktail at him and he didn't respond because he was so traumatised by the interrogations he went through in the hands of the military police," he added.