The Israeli military said it launched air strikes and artillery fire at targets in southern Gaza on Sunday, dimming hopes that a U.S.-mediated ceasefire would lead to lasting peace as Israel traded blame with Palestinian militant group Hamas.

Israel’s attacks on Sunday were the most serious test of an already fragile ceasefire, which took effect on October 11.

Israeli Prime Minister Benjamin Netanyahu said Israel would retaliate forcefully to Hamas attacks on its soldiers.

Hamas’ armed wing said in a statement that it remained committed to the ceasefire agreement in all of Gaza, adding that it was unaware of clashes in Rafah and that it has not been in contact with groups there since March.

“We affirm our full commitment to implementing all agreements, foremost among them the ceasefire across all areas of the Gaza Strip,” the Al-Qassam Brigades said.

Palestinian witnesses on Sunday separately told Reuters of explosions and gunfire in Rafah, tank fire in the southern town of Abassan near Khan Younis, an airstrike in the central town of Zawayda and explosions in the central town of Deir Al-Balah, which killed at least five people, according to medics at Al-Aqsa Hospital.

Witnesses in Khan Younis heard a wave of airstrikes launched into Rafah early on Sunday afternoon.

Gaza’s health ministry said on Sunday that Israeli attacks had killed at least eight people in the last 24 hours.

An Israeli military official said earlier on Sunday that Hamas had carried out multiple attacks against Israeli forces inside Gaza, including a rocket-propelled grenade attack and a sniper attack against Israeli soldiers.

“Both of the incidents happened in an Israeli-controlled area…This is a bold violation of the ceasefire,” the official said.

Defense Minister Israel Katz said the “yellow line” to where Israeli forces had pulled back under the ceasefire agreement would be physically marked and that any violation of the ceasefire or attempt to cross the line would be met with fire.

Senior Hamas official Izzat Al Risheq said on Sunday that the Palestinian militant group remained committed to the ceasefire, which he accused Israel of repeatedly violating.

The government media office in Gaza said on Saturday that Israel had committed 47 violations after the ceasefire deal, leaving 38 dead and 143 wounded.

“These violations have ranged from direct shooting at civilians, to deliberate shelling and targeting operations, as well as the arrest of several civilians,” the media office statement said.