Ukraine crisis: Rebels 'free 1,200 captives' - Poroshenko
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
Appeal for monitors
Mr Poroshenko said that "over the past four days, we have managed to secure the release of 1,200 of our captives", according to the Interfax-Ukraine news agency,
The announcement came after a ceasefire was reached in Minsk, Belarus, in talks brokered by the OSCE.
The negotiations involved former Ukrainian President Leonid Kuchma, leaders of the pro-Russian rebels, and a Russian delegate.
Mr Poroshenko appealed on Monday for the OSCE to send representatives to areas where the ceasefire has been broken.
Fighting in eastern Ukraine has left some 2,600 people dead since April.
Details of the EU sanctions are expected to emerge on Tuesday but the gas sector is not affected. Major state-owned oil firms are included such as Rosneft, which is already targeted by US measures.
Russia has warned that it could block international flights through its airspace if the EU goes ahead with new measures.
Diplomats say the new package will target Russian oil companies Rosneft and Transneft and the petroleum unit of state gas monopoly Gazprom.
Their access to financial markets will be restricted - a serious matter for Rosneft, which last month asked the Russian government for a $42bn (£25.2bn) loan.
Analysis: Andrew Walker, BBC economics correspondent
Rosneft calls itself the leader of the Russian petroleum industry. That makes it a very important player in the European Union's energy market. About 90% of the crude oil used in the EU is imported and Russia is, by a large margin, the biggest supplier.
The sanctions don't appear to directly affect that relationship. They would prevent Rosneft raising money in European financial markets.
But as crude oil is mainly transported by sea, if the trade were disrupted any losses from Russian suppliers could potentially be replaced. It would almost certainly be more expensive, but it could be done, up to a point.
Gas is another story, which may explain why Gazprom's main business is reported not to be on the new sanctions list. Russian gas is delivered to Europe by pipeline. There is a trade in gas transported by sea, but it would be very difficult to compensate for a major disruption of supplies from Russia.
The sanctions would also expand the visa bans and asset freezes on Russian officials and entities, including separatist leaders in Ukraine.
Earlier Russian Prime Minister Dmitry Medvedev warned that Moscow would respond "asymmetrically" to further sanctions.
A Russian airspace ban "could drive many struggling airlines into bankruptcy", he told a Russian daily.
12-point peace roadmap - key elements
- Ensure an immediate bilateral ceasefire
- Carry out decentralisation of power, allowing temporary local self-government in areas of Donetsk and Luhansk in eastern Ukraine under a "special status" law
- Immediately free all hostages and illegally detained persons
- Ensure monitoring on the Ukrainian-Russian border and a security zone
- Ensure the holding of snap local elections in Donetsk and Luhansk
- Remove illegal armed groups, military hardware, and all fighters and mercenaries from Ukrainian territory
- Pass a law against the prosecution and punishment of people over certain events in Donetsk and Luhansk region
Posted by the OSCE on its website (in Russian).