By Ahmed Kerdi and Maya Gebeily
BEIRUT, March 12 (Reuters) - Israeli airstrikes hit a building in the heart of Beirut on Thursday and Israel ordered residents out of another swathe of southern Lebanon, intensifying its offensive against the Iran-backed Hezbollah group.
The airstrike at around 5:30 p.m. (1530 GMT) hit a building in the Bachoura neighbourhood, around 1 km (mile) from the Lebanese government's Grand Serail headquarters in downtown Beirut.
Before the strike, the Israeli military issued a warning telling residents they were near a Hezbollah facility against which it intended to action.
Israel launched an air and ground offensive last week against Hezbollah, which launched attacks at Israel on March 2 that it said aimed to avenge the killing of Iran's supreme leader at the start of the U.S.-Israeli war on Iran.
Hezbollah has fired rockets and drones at Israel every day since, including its largest barrage late on Wednesday that triggered heavy Israeli strikes on Beirut's southern suburbs.
Israel has pounded Lebanon's south and east and the capital's southern suburbs, killing more than 600 people, according to Lebanese authorities. It has also ordered mass evacuations in those same areas, pushing more than 800,000 people out of their homes.
Israeli Defence Minister Israel Katz said the military had been instructed to expand its operations in Lebanon.
"We promised quiet and security to the communities of the north, and that is exactly what we will deliver," he said at a meeting with senior military officials.
(Reporting by Maya Gebeily in Beirut and Alexander Cornwell in Jerusalem; Writing by Maya Gebeily and Tom Perry; Editing by Timothy Heritage and Ros Russell)
