Sheikh Hassan Nasrallah, the leader of the Shia Muslim militant group Hezbollah, has called for fresh protests in Lebanon on Monday over film Innocence of Muslims.
The world needed to know Muslims “would not be silent in the face of this insult”, Sheikh Hassan Nasrallah said.
Protests at many US diplomatic missions have been continuing over the film, which was made in the US.
One person was reportedly killed in clashes between protesters and police in Pakistan on Sunday.
In a speech broadcast on Hezbollah’s al-Manar TV station, Sheikh Hassan Nasrallah called for demonstrations on several days over the coming week.
The first is scheduled to take place on Monday afternoon in a southern suburb of Beirut which is a Hezbollah stronghold.
Sheikh Nasrallah branded the video the most dangerous insult to Islam ever, worse, he said, than Salman Rushdie’s novel The Satanic Verses and the cartoons of the Prophet Muhammad, which were published in a Danish newspaper in 2005.
He said he had waited for the Pope to complete his three-day official visit to Lebanon before speaking out on the matter.
“Those who should be held accountable, punished, prosecuted and boycotted are those directly responsible for this film and those who stand behind them and those who support and protect them, primarily the United States of America,” Sheikh Hassan Nasrallah said.
He said that Arab and Islamic governments should press for an enforceable international law banning insults to Islam and other religions.
There have been protests over the film in Lebanon in recent days, but most have been reported from the northern city of Tripoli, which has a Sunni Muslim majority.
The obscure, poorly made film at the centre of the row, entitled Innocence of Muslims, depicts the Prophet Muhammad as a power-hungry and foolish man, and includes scenes of him having sex with his wife Khadija and other women.
The exact origins of the film are shrouded in mystery, although US authorities say they believe the film was made by Nakoula Basseley Nakoula, a convicted fraudster living in California.
On Monday, more than 1,000 people were reported to be taking part in a demonstration against the film in the Afghan capital, Kabul.
Some protesters were armed and have opened fire, but there were no reports of casualties, a senior security official said.
Two police vehicles have been set on fire on the Jalalabad road, home to NATO and US military bases.
Sunday’s clashes in Karachi, Pakistan’s biggest city, occurred when protesters attempted to break through a barricade to the US consulate.
Police used tear gas and fired warning shots into the air in response to stone-throwing protesters.
A spokesman for the group that organized the rally told the Associated Press news agency that a protester had been killed in the clashes. Several other people were injured.
The US embassy in Islamabad announced on its Twitter feed that “all American personnel are safe and accounted for” at the consulate and thanked Pakistani police for their efforts in protecting it.
In the Danish capital, Copenhagen, a few hundred people held a vocal demonstration outside the US embassy.
Protesters directed invective not just towards the controversial video, but also at US military involvement in the Middle East and Afghanistan.
Crowds also gathered outside the US consulate in the Dutch capital, Amsterdam.
Anti-Islamic Dutch politician Geert Wilders, whose party lost many of its seats in last week’s elections, has posted a link to the video on his website and encouraged his followers to do the same.
Also on Sunday, the president of Libya’s interim assembly said some 50 people had been arrested in connection with last week’s deadly attack on the US consulate in Benghazi.
Mohamed Magarief told CBS News he had “no doubt” the attack was pre-planned, and that some of those who took part were from outside Libya.
US Ambassador Chris Stevens and three other US consulate staff were killed in the attack.
However, US Ambassador to the UN Susan Rice told ABC America’s “current best assessment” was that “this began as a spontaneous, not a pre-meditated, response” to earlier protests over the film in the Egyptian capital, Cairo.
The violence in Benghazi was followed by a string of attacks on US consulates, embassies and business interests across the Middle East and north Africa. British, Swiss, German and Dutch properties have also been targeted.
Al-Qaeda in the Arabian Peninsula has called for fresh attacks against Western embassies, describing the recent unrest as “a great event”, and urging protesters to unite to “expel the embassies of America from the lands of the Muslims”.