PARIS (AFP) - French President Francois Hollande said on Sunday that evidence indicated Syrian President Bashar al-Assad's regime had carried out chemical weapons attacks on its own people last week.

Mr Hollande said there was "a body of evidence indicating that the August 21 attack was chemical in nature, and that everything led to the belief that the Syrian regime was responsible for this unspeakable act".

The French president called for UN weapons inspectors to be given access to suspect sites "without delay and without any restrictions whatsoever", in a statement released by his office after he held telephone talks on the situation in Syria with Australian Prime Minister Kevin Rudd.

A separate statement issued after Mr Hollande held phone talks with British Prime Minister David Cameron said the two leaders "unreservedly condemned the use of chemical weapons in Syria".

The presidency said Mr Hollande and Mr Cameron have agreed to hold talks soon on how to respond to the regime's "intolerable act", which it said France was determined "not to let... go unpunished."

The Syrian opposition accuses Mr Assad's forces of killing more than 1,300 people on Wednesday in chemical attacks in the east and southwest of Damascus.

Doctors Without Borders said 355 people died this week of "neurotoxic" symptoms.

Syria has denied the accusations.

Urine, blood and hair samples collected in Damascus on Wednesday were being transported to various European capitals including Paris for testing, French newspaper Le Journal du Dimanche reported on Sunday.

The results of previous samples taken from Syria in May led France to accuse the regime of using the nerve gas sarin.

Defence Secretary Chuck Hagel said on Sunday that the US military was ready to take action against President Assad's regime if ordered to by US President Barack Obama.