Islamic State militants attacked Syrian army troops with mustard gas in an offensive against a Syrian military airport in the eastern province of Deir al-Zor that borders Iraq, state media said on April 4.

The first migrants deported from Greek islands under a disputed EU-Turkey deal were shipped back to Turkey on April 4 in a drive to shut down the main route used by more than a million people fleeing war and poverty to reach Europe in the last year.

Dutch voters will decide on April 6 whether to support a European treaty deepening ties with Ukraine in a referendum that will test sentiment toward Brussels ahead of Britain's June Brexit vote and could also bring a boost for Russia.

Azerbaijan said on April 3 it would stop fighting Armenian-backed separatists over the breakaway Nagorno-Karabakh region after two days of clashes, but the other side denounced Baku's gesture as hollow and said violence was continuing.

Syrian and allied forces backed by Russian air strikes drove Islamic State militants out of the town of al-Qaryatain on April 3 after encircling it over the past few days, Syria's military command said.

Brussels Airport reopened to a thin stream of passengers on April 3, 12 days after suicide bombers destroyed its departure hall and killed 16 people.

Clashes erupted between troops from Azerbaijan and the rebel Nagorno-Karabakh region on April 2, the two sides said, disputing who had violated a fragile ceasefire again.

Greece demanded an explanation from the International Monetary Fund on April 2 after an apparent leaked transcript suggested the IMF may threaten to pull out of the country's bailout as a tactic to force European lenders to more offer debt relief.

The Democratic People's Republic of Korea (DPRK) will pursue its nuclear and ballistic missile program in defiance of the United States and its allies, a top Pyongyang envoy said on April 1, adding that a state of "semi-war" now existed on the divided Korean peninsula.

Migrants protested on a Greek island and rights groups raised legal objections on April 1 three days before a disputed EU deal to return rejected asylum seekers from Greece to Turkey was due to go into action, with neither side completely ready.