The leader of Lebanese terror group Hezbollah, Sheikh Hassan Nasrallah, was hospitalized in the Al-Rasoul al-Azam Hospital in Beirut’s Dahiyeh quarter Thursday, where he underwent a “delicate” surgical procedure, Lebanese media reported.

Scores of armed Hezbollah fighters surrounded the medical complex as the procedure was taking place in order to protect the Shiite leader from potential attack. Details regarding the surgical procedure were not reported.

Last year, Nasrallah, 53, reportedly traveled to Tehran for treatment of an unspecified illness. His health was said to have greatly deteriorated after the illness was discovered. Lebanon’s Sawt Beirut International radio station, which is affiliated with political factions opposed to Hezbollah, claimed Nasrallah had a cancerous tumor.

Hezbollah, on its part, denied that its leader had taken ill. “Hassan Nasrallah is in good health,” Hezbollah officials were quoted as saying.

The Shiite leader’s unspecified medical condition has reportedly prevented him from making media appearances in recent weeks. However, Hezbollah officials stated that Nasrallah will address his supporters in a televised speech next Thursday.

Yifa Yaakov and Elhanan Miller contributed to this report.