The pro-Iran group has called for a huge turnout when Nasrallah, killed in a September Israeli strike, is laid to rest in the Lebanese capital on Sunday.

"Iraqi Airways will increase its flights to Beirut from one flight a day to two, starting on February 20," said transport ministry spokesperson Maytham al-Safi, citing heightened demand ahead of the funeral.

An Iraqi airline official told AFP that "all seats on Iraqi Airlines flights from Baghdad to Beirut are booked".

A source from Lebanon's Middle East Airlines (MEA) reported increased flights between Baghdad and Beirut from Friday to Tuesday.

The airlines' websites show that Iraqi Airways flights are fully booked until Sunday, with MEA nearly sold out.

Iraqi lawmakers and officials are expected to attend Nasrallah's funeral privately, an Iraqi official said.

Representatives from pro-Iran Iraqi factions, Hezbollah's longstanding allies in the Tehran-led "axis of resistance", are also expected to participate.

Beirut airport will close for four hours during the funeral.

Hezbollah has said 79 countries would be involved in the commemoration, either officially or through "popular" support.

Sunday's funeral will also honour Hashem Safieddine, a senior Hezbollah figure who had been chosen to succeed Nasrallah, before he was killed in an Israeli strike in October.

After decades at the helm of the group once seen as invincible, the killing of the charismatic Nasrallah sent shock waves across Lebanon and the wider region.

Since Nasrallah's death, portraits of him, either alone or alongside other slain pro-Iran commanders, have been displayed throughout Baghdad and other areas of the Shiite-majority country.

On Sunday afternoon, thousands are expected to attend a "symbolic" procession for Nasrallah in Baghdad's northwestern neighbourhood of Kadhimiya, which is home to a Shiite shrine.