Nearly 500 Nigerian soldiers have fled into Cameroon after severe clashes with Boko Haram fighters, according to Cameroon’s army.

Spokesman Lt Col Didier Badjek told the BBC that the soldiers have been disarmed and are being accommodated in schools in Maroua, around 80km from the Nigerian border.

Thousands of civilians are also thought to have crossed the border into Cameroon. Clashes are reported to be ongoing in the border town of Gamboru Ngala.

Ukrainian troops have engaged in clashes with Russian troops which crossed the border in the southeast of the country.

Ukrainian military spokesperson Andriy Lysenko said Russian military vehicles with the insignia of the self-proclaimed Donetsk People’s Republic “violated the state border of Ukraine” in the southern part of Donetsk region.

Lysenko said at least 10 tanks, two armored vehicles and two trucks from Russia crossed into the country on Monday soon after which they engaged in clashes with a Ukrainian military border unit.

The Syrian government says it will help the US fight Islamic State militants, who have seized huge swathes of land across Syria and Iraq.

Foreign Minister Walid Muallem said Syria was "the centre of the international coalition to fight Islamic State", adding that the US must coordinate with Syria before launching attacks in its territory.

"Anything outside this is considered aggression," he said.

Over 300 Holocaust survivors and descendents have signed a letter condemning Israel’s “genocide” in Gaza.

The International Jewish Anti-Zionist Network (IJAN) said in a press release that it penned the letter in response to “an inflammatory ad campaign”, in which prominent Holocaust survivor Elie Wiesel compares the killing of children during the Holocaust to Hamas’ actions in Gaza.

Boko Haram’s leader declared an Islamic caliphate, in northeast Nigeria town seized by the militants last month.

“Thanks be to Allah who gave victory to our brethren in (the town of) Gowza and made it part of the Islamic caliphate,” Abubakar Shekau said in a video obtained by the Agence France Presse.

The news comes as 35 Nigerian police officers training in the northeast regions, were reported missing by the government, after Boko Haram attacked their training facilities.

Iran’s elite Revolutionary Guard said that it brought down an Israeli stealth drone above one of its nuclear enrichment sites on Sunday, reports AlJazeera.

“The downed aircraft was of the stealth, radar-evasive type and it intended to penetrate the off-limit nuclear area in Natanz... but was targeted by a ground-to-air missile before it managed to enter the area" said a statement by the Revolutionary Guards.

Britain has appointed a security envoy to Iraq’s Kurdistan region to bolster efforts to defeat Islamic State militants reports the Associated Press.

The Prime Minister’s office, on Sunday, said  the government would be sending night vision equipment, body armour and other non-lethal military gear to Kurdish forces in northern Iraq.

The Defence Secretary Philip Hammond added that the Royal Air Force would begin to ship ammunition and weapons of types used by the Kurdish forces.

Ukrainian President Petro Poroshenko announced $3bn will be spent on re-equipping his country’s army.

Speaking on the Ukrainian independence day, the president said that his country was fighting "a war against external aggression, for Ukraine, for its freedom, for its people, for independence".

"It is clear that in the foreseeable future, unfortunately, a constant military threat will hang over Ukraine. And we need to learn not only to live with this, but also to be always prepared to defend the independence of our country," he said, according to Reuters.