Ukraine crisis: Rebels 'free 1,200 captives' - Poroshenko

Petro Poroshenko: "We should have the representatives of the OSCE - just for the quick reaction if anything goes wrong"

Pro-Russian rebels in Ukraine have released 1,200 prisoners, President Petro Poroshenko has said.

The releases followed Friday's ceasefire deal, he said, which included an exchange of prisoners.

He was speaking during a visit to the strategic south-eastern port city of Mariupol, which has come under shelling from pro-Russian rebels in recent days.

Mr Poroshenko announced his arrival in a tweet: "Mariupol is Ukraine. We will not surrender this land to anyone."

Meanwhile, EU member states have agreed to impose a new package of sanctions against Moscow, to come into force in the coming days.

EU Council President Herman van Rompuy said the measures were aimed at "promoting a change of course in Russia's actions destabilising eastern Ukraine".

But the 28-member bloc is being deliberately vague about when they will come into force, to allow time to assess the implementation of the ceasefire, BBC Europe correspondent Chris Morris reports.

The ceasefire appears to be holding, although the head of the Organization for Security and Cooperation in Europe (OSCE), which brokered the deal, described it on Monday as "shaky".

Before the truce came into place, pro-Russian separatists made big gains in eastern Ukraine and seized territory a few miles outside Mariupol.

Mr Poroshenko said during his visit on Monday that the city's defences would be reinforced and that rebels would suffer a "crushing defeat" if they advanced on the city.

Mariupol is the last city in Donetsk region still held by the Ukrainian government and is a strategic port on the route to Crimea, the peninsula annexed by Russia in March.

Russia has repeatedly denied accusations by Ukraine and the West that it has been sending troops into Donetsk and Luhansk regions to help the rebels, who want to establish an independent state.

Also on Monday:

• Mr Poroshenko and Russian President Vladimir Putin spoke on the phone to discuss "steps to facilitate a peaceful resolution of the situation", the Kremlin said
• Mr Poroshenko said Ukraine is to receive "direct supplied of modern weaponry" from Nato countries, according to Interfax-Ukraine. Nato countries have previously denied similar claims