Israel's military said its troops reached the sea side of the Gaza Strip, leaving the enclave's densely populated main city surrounded.

The move separated the strip's north and south and raised speculation that full-scale street fighting would begin.

Air strikes continued from Sunday night through Monday morning in the Gaza Strip.

Israel's military said on Monday that tunnels and watchtowers were included in 450 Hamas positions it attacked. It also said it seized a military base.

Palestinian media reported that dozens of people were killed by Israeli bombings of the Nuseirat refugee camp in central Gaza and the southern city of Rafah.

Military spokesperson Daniel Hagari told reporters on Sunday that troops had reached the coastline in the southern part of Gaza City, encircling the area.

He also said, "There is north Gaza and south Gaza," suggesting the area has been divided militarily.

Israel is still urging Gaza residents in northern areas to evacuate to the south.

An escalation of street battles in Gaza City could raise the death toll. Almost 10,000 people have been killed in the Gaza Strip in the past few weeks.

Meanwhile, fighting between the Israeli military and Lebanon-based Shia militant group Hezbollah is heating up in northern Israel.

In Lebanon, media reported that an Israeli attack killed three children and their grandmother on Sunday.

In Israel, an antitank shell fired from Lebanon hit a community near the border, killing one civilian. Another shell set a parked vehicle ablaze in the northern Israeli town of Kiryat Shmona.

Hezbollah leader Hassan Nasrallah indicated on Friday that the group would step up attacks on Israel if civilians fall victim to attacks.

Israel may face intensified fighting on two fronts, one with Hamas in the south and the other with Hezbollah in the north.