Israeli warplanes struck suspected Hamas military targets in the Gaza Strip before dawn on Friday following rocket fire from the blockaded Palestinian territory.

Fighter jets and other aircraft struck a "weapons manufacturing site and underground infrastructures" operated by Islamist group Hamas, which has controlled the territory since 2007, the Israeli army said.

Hamas reported no casualties from the Israeli strikes on the Nuseirat refugee camp and the southern city of Khan Yunis.

Two rockets had been launched at Israel late Thursday, without causing any casualties or damage.

One was intercepted by Israeli air defences, while the other hit open ground, the army said.

The last reported rocket attack from Gaza was on Tuesday night.

It came after the army announced it had found a new tunnel that crosses "dozens of metres (yards) into Israel" from Gaza.

The next day the army said the tunnel belonged to Hamas.

Authorities have discovered some 20 tunnels originating in Gaza since 2014, army spokesman Jonathan Conricus said this week.

Israel has fought three wars with Hamas since the Islamists ousted loyalists of Palestinian president Mahmud Abbas from the territory in 2007 and there have been numerous smaller flare-ups.

An informal truce brokered by Egypt and the United Nations, with the financial support of gas-rich Qatar, has been in force since late 2018.

It has been broken several times but has been restored on each occasion.