JERUSALEM — In a rare step, a leading Israel human rights group on Wednesday urged Israeli forces to disobey open-fire orders unless Gaza protesters pose an imminent threat to soldiers’ lives.

B’Tselem said the appeal is a last-ditch attempt to prevent more bloodshed on the volatile Gaza-Israel border.

Nineteen Palestinians have been killed by Israeli fire in Gaza since last Friday, including 14 in border protests. More demonstrations are expected along the border this Friday.

B’Tselem has never before called on soldiers to refuse orders, but believes firing on Palestinians who pose no imminent threat to the lives of Israeli forces is ‘‘manifestly illegal,’’ said spokesman Amit Gilutz.

‘‘As long as soldiers in the field continue to receive orders to use live fire against unarmed civilians, they are duty-bound to refuse to comply,’’ the group said.

The Israeli military has said its tough response is justified because the protests were organized by Hamas, an Islamic militant group sworn to Israel’s destruction.

It said soldiers targeted only ‘‘instigators’’ who burned tires or threw stones and firebombs at the border fence. The military accused Hamas of using the large crowds as cover to carry out attacks.

In one instance, a pair of gunmen approached the border, and the army said protesters tried to plant explosives along the fence in several instances. But in other incidents, some caught on video, those who were shot appeared to have been unarmed and not actively involved in violence.

B’Tselem said that while Israel has the right to defend its border, it is still bound by international norms for the use of live fire.

The group said that simply approaching the fence, and even damaging it, does not provide grounds for using lethal force, and that Israel had other options for dispersing the crowds.

‘‘The provisions limit its use to instances involving tangible and immediate mortal danger, and only in the absence of any other alternative,’’ the group said. ‘‘Israel cannot simply decide that it is not bound by these rules.’’

Israel’s military is the country’s most respected institution, and such criticism, even from a dovish group, is relatively rare. B’Tselem said it would be publishing newspaper ads and taking other steps to publicize its campaign.

The Israeli military did not immediately respond to a request for comment.

But the country’s defense minister, Avigdor Lieberman, said Tuesday that the military will not change its tactics and warned that anyone who approaches the border is risking his life. The tough comments raised the possibility of more bloodshed Friday, when another mass protest is expected.

On Wednesday, the head of the Arab League called on the International Criminal Court in The Hague to investigate the deaths of Palestinians in Gaza since Friday.

Hamas is organizing six weeks of on-and-off border protests in what it says is a campaign to draw attention to a crippling border blockade.

Both Israel and Egypt have maintained a blockade since Hamas seized control of Gaza in 2007 in an attempt to weaken the militant group.

Israel said Wednesday that it had arrested 10 Palestinians suspected of planning an attack on a navy ship off Gaza.

Protests are planned through May 15, the 70th anniversary of Israel’s founding. The date is mourned by Palestinians; hundreds of thousands were uprooted in the 1948 war over Israel’s creation.