Ukraine crisis: Fresh prisoner swaps expected

More prisoner exchanges are expected between Ukraine and pro-Russian rebels in the east - a day after the two sides swapped hundreds of captives, the BBC reported.

Ukrainian officials say they are hoping that four soldiers will be freed. The number of militants due to be released has not been confirmed.

On Friday, Ukraine said 146 of its soldiers had been freed for 222 rebels.

Meanwhile, Ukraine froze vital bus and rail links with Crimea, its southern peninsula annexed by Russia in March.

Crimea has no land corridor to Russia, and relies on a ferry in the Azov Sea and flights from Russia.

The peninsula - which is also heavily dependent on Ukraine's power supplies - has also seen blackouts in recent days.

Kiev says it has to limit supplies, because Ukraine itself is experiencing power shortages.

In a separate development, the world's two largest credit and debit card companies, Visa and Mastercard, said on Friday they could no longer support bank cards being used in Crimea, following fresh US sanctions imposed this month.

The moves come ahead of the traditional holiday season in the region, when people travel to be with their families for New Year.

Russian media reported that a number of people in Crimea on Friday were unable to withdraw cash or pay for goods bought in local supermarkets.