At least five people were killed by an Israeli strike in Beirut, Lebanon's Health Ministry said in the early hours of Thursday morning.
Another eight people were wounded in the attack, the ministry added.
There was no warning issued ahead of the strike, the Associated Press reported.
The Hezbollah-run Al-Manar TV channel said the strike targeted a center of Hezbollah's health unit.
Hezbollah is an Iran-backed Shiite political party and militant group in Lebanon. It is considered a terrorist organization by the US, Germany and several Sunni Arab countries, while the EU lists its armed wing as a terrorist group.
Lebanon's hospitals 'overwhelmed' by injured patients
Lebanon's healthcare system is struggling to keep up with the number of people injured in fighting between Israel and Hezbollah, World Health Organization chief Tedros Adhanom Ghebreyesus said late on Wednesday.
"The death toll in Lebanon is rising, and hospitals are overwhelmed with the influx of injured patients," Tedros said on social media.
"The health system has been weakened by successive crises and is struggling to cope with the immense needs."
More than 1,000 people have died in Lebanon amid fighting that erupted last week and included Israeli strikes on Beirut, according to Lebanese authorities.
The Lebanese Health Ministry said Israeli strikes killed 46 people and injured 85 others on Wednesday alone.
"Any further escalation of the conflict will have catastrophic consequences for the region," Tedros added.
"The best medicine is peace."
IDF issues evacuation warning for southern Beirut
The Israel Defense Forces (IDF) issued fresh evacuation orders for several parts of southern Beirut in the early hours of Thursday morning.
The warning was directed at residents of the Haret Hreik, Burj al-Barajneh and Hadath Gharb areas specifically.
"You are located near facilities and interests belonging to Hezbollah, which the army will act against in the near future," Israeli military spokesperson Avichay Adraee said on social media.