* Israeli air strike kills 2 Palestinians on motorcycle
* Palestinians keep up rocket fire on Israel
* No sign warring sides returning soon to truce talks
By Nidal al-Mughrabi and Jeffrey Heller
GAZA/JERUSALEM, Aug 24 (Reuters) - Israel launched more air strikes on Gaza on Sunday after taking its military campaign to a new level by flattening a 13-storey apartment tower following a warning to residents to evacuate.
Palestinian militants kept up their cross-border rocket fire in what has become a conflict of attrition that has defied attempts by regional power Egypt to broker a durable truce in fighting now in its seventh week.
An Israeli air strike killed two people on a motorcycle in Gaza, medical officials said, hours after a bombing attack brought Al Zafer Tower in Gaza City crashing to the ground.
It was the first time Israel had destroyed so large a structure in the Gaza war. It launched the attack a day after a mortar bomb killed a four-year-old Israeli boy, and Israel's president attended his funeral on Sunday near the Gaza border.
The Israeli military said the building contained a command centre belonging to Hamas militants, and that it had fired a non-explosive warning rocket on Saturday, 10 minutes before attacking.
Local residents said the high-rise housed 44 families. Medical officials said 17 people were wounded in the Israeli strike.
Egypt called on Israel and the Palestinians on Saturday to halt hostilities and return to talks. But there was no sign that negotiations, last held before a ceasefire collapsed on Tuesday, would resume any time soon.
Israel also faced rocket fire from the north on Saturday.
Two missiles launched from Lebanon struck Israel's Galilee. Lebanese and Israeli sources said it was not initially clear who was behind the attack, which caused no casualties or damage.
At least five rockets fired from Syria landed at various locations on the Israeli-occupied Golan Heights, the Israeli army said. All fell in open areas. It was also not immediately known who launched them.
Late on Saturday, an Israeli air strike destroyed a commercial centre in the southern Gaza town of Rafah and three people were hurt, local medical staff said.
Palestinian health officials say 2,085 people, most of them civilians and more than 400 of them children, have been killed in the Gaza Strip since July 8, when Israel launched an offensive with the declared aim of ending Palestinian rocket fire into its territory.
Sixty-four Israeli soldiers and four civilians in Israel have been killed.
Hamas has said it will not stop fighting until the Israeli-Egyptian blockade on Gaza is lifted. Both Israel and Egypt view Hamas as a security threat and are reluctant to make sweeping concessions without guarantees weapons will not enter the economically crippled enclave.
The Cairo talks had aimed to secure a lasting deal to open the way for reconstruction aid to flow into the Gaza territory of 1.8 million people, where thousands of homes have been destroyed.
The United Nations says about 400,000 Gazans have been displaced in the longest and deadliest violence between Israel and the Palestinians since the second Intifada, or Palestinian uprising, a decade ago.
(Additional reporting by Maayan Lubell and Ori Lewis in Jerusalem and Sylvia Westall in Beirut; Writing by Jeffrey Heller; editing by Ralph Boulton)