From Nigeria to Athens, Muslim protests rumble on

* Flags burned, but protests mostly peaceful

* Police use teargas against Muslims protesters in Athens

* Anger simmers as world gathers at UN in New York

By Robin Pomeroy

DUBAI, Sept 23 (Reuters) - Muslims protested in Nigeria, Iran, Greece and Turkey on Sunday to show anti-Western anger against a film and cartoons insulting Islam had not dissipated.

As delegates from around the world gathered in New York for a U.N. General Assembly where the clash between free speech and blasphemy is bound to be raised, U.S. flags were once again burning in parts of the Muslim world.

Iranian students chanted "Death to America" and "Death to Israel" outside the French embassy in Tehran in protest at the decision by satirical magazine Charlie Hebdo to publish cartoons of the Prophet Mohammad, days after widespread protests - some deadly - against a film made in the United States.

Shi'ite Muslims in the Nigerian town of Katsina burned U.S., French and Israeli flags and a religious leader called for protests to continue until the makers of the film and cartoons are punished.

In Pakistan, where fifteen people were killed in protests on Friday, a government minister has offered $100,000 to anyone who kills the maker of the short, amateurish video "The Innocence of Muslims". Calls have increased for a U.N. measure outlawing insults to Islam and blasphemy in general.

In Athens, some protesters hurled bottles of water, stones and shoes at police who responded with teargas. Calm returned when demonstrators interrupted the protest to pray.

ON ALERT

Protests around the world were relatively small and calm, but Western embassies remained on alert after the U.S. ambassador to Libya and three other Americans were killed in one of the first protests, on Sept. 11.

The upsurge of Muslim anger - just weeks before U.S. elections - have confronted President Barack Obama with a setback yet in his efforts to keep the "Arab Spring" revolutions from fuelling a new wave of anti-Americanism.

In U.S. ally Turkey, a secular Muslim state often seen as a bridge between the Islamic world and the West, protesters set fire to U.S. and Israeli flags on Sunday.

"May the hands that touch Mohammad break," chanted some 200 protesters before peacefully dispersing.

"We will certainly not allow uncontrolled protests, but we will not just grin and bear it when Islam's prophet is insulted," Prime Minister Tayyip Erdogan told party members at the weekend.

"The protests in the Muslim world must be measured, and the West should show a determined stance against Islamophobia."