BEIRUT -- Hezbollah was pulled more deeply into Syria's civil war as 28 guerrillas from the Lebanese Shia militant group were killed and dozens more wounded while fighting rebels, Syria activists said Monday.
The intense battle drove rebels from large parts of the town of Qusair, part of a withering government offensive aimed at securing a strategic land corridor from Damascus to the Mediterranean coast.
Hezbollah-affiliated hospitals in Lebanon urged blood donations through mosque loudspeakers and ambulances raced along the Damascus road in a stark indication of the group's increasingly prominent role in Syria.
The overt Hezbollah involvement -- several funerals for group members were held Monday in Lebanon -- edges the war further into a regional sectarian conflict pitting the Middle East's Iranian-backed Shia axis against Sunnis.
It also raised tensions considerably in Lebanon, where Hezbollah has come under harsh criticism for its involvement in the civil war next door.
A staunch ally of Syrian President Bashar Assad, Hezbollah is heavily invested in the survival of the Damascus regime and is known to have sent fighters to aid government forces.
The Iranian-backed group's growing role in the conflict also points to the deeply sectarian nature of the war in Syria, in which a rebellion driven by the country's Sunni majority seeks to overthrow a regime dominated by Assad's Alawite sect, an offshoot of Shia Islam.
Clashes continued for the second day in the northern city of Tripoli, Lebanon, where Sunnis and Alawites battled in a direct spillover from the fighting in Qusair.
The Britain-based Syrian Observatory for Human Rights, which tracks Syria's civil war, said that more than 70 Hezbollah fighters have also been wounded in the fighting around Qusair.
A White House official said President Barack Obama telephoned Lebanon's president and expressed concern about Hezbollah's "active and growing role in Syria, fighting on behalf of the Assad regime, which is counter to the Lebanese government's policies."