Israel has launched some of the heaviest airstrikes to date on Beirut, the Lebanese capital, before an expected ceasefire in its war with Hezbollah.

The Israeli military began attacking areas of Beirut dominated by the Lebanese militia early on Tuesday before issuing a flurry of 20 evacuation calls – its widest warning to civilians since hostilities escalated into full-blown war in late September.

At least 20 strikes had hit Beirut by Tuesday afternoon, as well as 30 sites across southern Lebanon. At least three people were killed and 26 wounded in southern Beirut, the Lebanese health ministry said, with the toll expected to rise.

The Israeli army said it was carrying out “a widespread attack” on Hezbollah targets, including an aerial defence unit centre, an intelligence centre, rocket launching sites and weapons storage facilities.

A statement said there were also army raids in the Litani River region – the deepest ground push into Lebanon so far – as Israel appeared to try to shore up its military gains in the conflict before a truce, which may be implemented as early as Wednesday.

Hezbollah barrages of rockets and drones into northern Israel on Tuesday seriously injured two civilians and one soldier. Restrictions were tightened in response to increase in fighting, barring large gatherings and closing schools in several areas.

Israel’s security cabinet is scheduled to meet on Tuesday afternoon to vote on the proposal, which is expected to pass despite opposition from far-right allies of the prime minister, Benjamin Netanyahu.

Unconfirmed reports said that the US president, Joe Biden, and his French counterpart, Emmanuel Macron, were expected to announce the deal on either Tuesday night or Wednesday.

Israel appears to have come to the table after suffering US weapons shortages, as well as warnings from the Biden administration that a failure to agree a ceasefire under US auspices would lead Washington not to use its veto to block a UN security council resolution ordering a ceasefire. A UN-mandated truce would be unlikely to be as amenable to Israel’s demands.

However, the country has vowed that it will act forcefully in the event of any Hezbollah infraction of the deal. “We will act against any threat, anytime and anywhere,” Israel’s newly appointed defence minister, Israel Katz, told the UN’s special envoy for Lebanon, Jeanine Hennis-Plasschaert, according to a statement from his office.

Iran, Hezbollah’s patron, has reportedly approved the ceasefire deal under discussion, eager to avoid further damage to its most important deterrent force against Israel. Importantly for Israel, Hezbollah dropped its demand that a ceasefire in Lebanon is contingent on ending the fighting in Gaza.

The current deal is based on UN security council resolution 1701, which ended the 36-day Israel-Hezbollah war of 2006, but was never fully implemented.

Under its terms, Israel will withdraw entirely from southern Lebanon, while Hezbollah would move its heavy weaponry north of the Litani River, about 16 miles (25km) north of the border. During a 60-day transition phase, the Lebanese army would deploy to the buffer border zone alongside the existing UN peacekeeping force. Longstanding border disputes will be discussed after the 60-day withdrawal period.

The process will be monitored by a US-led supervisory mechanism that would act as a referee on infringements. A letter of assurance that is not formally part of the deal reportedly guarantees US support for Israeli freedom of action if Hezbollah attacks Israel again or moves its forces or weaponry south of the Litani.

Biden, wary of regional escalation that could draw in Iran, has been trying to broker a truce between Israel and Hezbollah for months. The conflict began 13 months ago when the powerful Lebanese militia began firing rockets and shells at Israel a day after the Palestinian group Hamas attacked Israel, triggering the Gaza war.

The conflict escalated in late September, when hundreds of Hezbollah pagers exploded in an attack attributed to Israel. Israel then killed much of Hezbollah’s leadership in airstrikes, and launched a ground invasion of southern Lebanon.