MOSCOW (REUTERS) - Russian President Vladimir Putin called on Friday for a long-term ceasefire in Ukraine to allow for talks between representatives of Kiev and eastern regions where rebels are waging an armed insurgency.

Ukrainian President Petro Poroshenko has warned a ceasefire now in place may not be extended beyond Friday night when it is due to expire if peace talks with pro-Russian separatists fail to yield a favourable outcome.

"Most important is the securing of a long-term ceasefire as a necessary condition for substantive talks between the authorities in Kiev and representatives of the southeastern regions," Mr Putin said.

"We sincerely strive to help the peace process," he told delegates at a diplomatic ceremony in the Kremlin.

Western governments have piled pressure on Mr Putin to take steps to disarm the rebels that Kiev accuses of numerous breaches of the truce aimed at giving the two sides time to find a political solution to the crisis.

Mr Putin also said that the violence in Ukraine had forced tens of thousands of Ukrainians to seek refuge abroad, including in Russia.

Separately, the United Nations' agency for refugees reported on Friday that some 110,000 people have fled to Russia from Ukraine while more than 54,000 have been displaced inside the conflict-torn country.

"Since the start of 2014, 110,000 Ukrainians have arrived in Russia," said Ms Melissa Fleming, chief spokeswoman of the UN High Commissioner for Refugees, adding that most were thought to be from the east of the country.

Within Ukraine itself, 16,400 people have fled their homes in the east in the past week alone, taking the total number of internally-displaced to 54,400, Ms Fleming told reporters.