Israel bombarded the southern Gaza town of Rafah on Saturday as troops searched for an officer they believe was captured by Hamas in an ambush that shattered a humanitarian ceasefire and set the stage for a major escalation of the 26-day-old war, agency reports from Gaza City and Gaza Strip said.

The Israeli military has said it believes the soldier was grabbed in a Hamas ambush about an hour after an internationally brokered ceasefire took effect on Friday morning. The Hamas military wing on Saturday distanced itself from the soldier’s alleged capture, which has prompted widespread international condemnation. President Barack Obama, U.N. chief Ban ki-Moon and others have called for his immediate and unconditional release.

At least 35 Palestinians were killed in the bombardment and shelling in and around the city of Rafah early on Saturday, said Palestinian health official Ashraf al-Kidra, adding that the area’s main hospital was evacuated because of the strikes.

Elsewhere in Gaza, Palestinian officials reported more than 150 airstrikes including one against the Islamic University in Gaza City. Heavy shelling continued along the border areas. The fiercest battles took place near the site of Friday’s attack and purported abduction, near Rafah, about 3 kilometres inside the strip and close to the borders with Israel and Egypt.

The Hamas military wing said in a statement on its website that it is “not aware until this moment of a missing soldier or his whereabouts or the circumstances of his disappearance”.

The group said it believes the soldier might have been killed in a clash with Hamas fighters about an hour before the start of the 8.00 a.m. ceasefire.

The Israeli military declined comment on the statement.

The disappearance of the soldier, 2nd Lt. Hadar Goldin, and the heavy clashes that followed it shattered an internationally brokered ceasefire that was to have been in place for three days and open the way for talks in Cairo on a more sustainable truce.

Israel and Hamas have accused each other of violating the humanitarian pause.

Israeli reserved soldiers direct a Merkava tank to cross a road in the southern Israel as it advances towards the Israel-Gaza border.