French President Francois Hollande has warned Prime Minister Theresa May that the start of Brexit negotiations cannot drag on.

Mr Hollande issued the warning after talks in Dublin with Taoiseach Enda Kenny and only hours before he meets the new PM in Paris.

"Should the negotiations be shorter? The most important thing is that they should not drag on," the president said.

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"The sooner the negotiations are open the better, and the shorter the better."

The French president said suggestions have been raised that Brexit talks will start as late as December.

"It's a decision that was taken by the British people," Mr Hollande said.

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"Firstly it was the British who will have to bare the consequences. Europe will try its best to give its best relationship with the UK.

"But there's a time the politicians have to accept this vote. They have to accept the consequences."

Mr Hollande's trip to Dublin was arranged before last Friday's Bastille Day atrocity in Nice.

Eighty-four people were killed when Tunisian Mohamed Lahouaiyej Bouhlel drove a truck into crowds enjoying celebrations and fireworks over the Promenade des Anglais.

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Another 15 people remain critically ill in hospitals.

While Mr Hollande's trip to Dublin has been scaled back in the wake of the terror attack, he has retained a commitment to meet President Michael D Higgins.

He will be back in Paris for talks with Mrs May this evening.

Defence, deepened security and counter-terrorism measures across Europe were also discussed.