KIEV--Top European Union officials were meeting Monday with Ukrainian President Petro Poroshenko in talks aimed at speeding economic and political reforms, as heavy fighting around a key town in the country's east again tested a fragile cease-fire between Kiev's forces and pro-Russia separatists.

European Commission President Jean-Claude Juncker arrived in Kiev from Luxembourg in the morning and immediately joined Mr. Poroshenko and European Council President Donald Tusk for talks at the presidential office.

They are expected to be joined by Ukrainian Prime Minister Arseniy Yatsenyuk. A number of other senior Brussels officials will be in Kiev to attend a National Reform conference on Tuesday, including the EU's point people on energy and economic issues.

European officials have said they would stress the importance of pressing ahead on reforms, including the thorny issue of decentralization of powers to the eastern provinces currently controlled by the separatists.

Under the latest version of the cease-fire deal reached in the Belarusian capital of Minsk in February, Kiev pledged to offer greater autonomy to the eastern regions, as well as to restore economic and other links. So far, however, progress on those areas has been slow.

Fighting has subsided across most of the front line. But monitors from the Organization for Security and Cooperation in Europe reported late Sunday that they had witnessed some of the heaviest fighting since February around Shyrokyne, a strategic town on the outskirts of Mariupol, the largest city in the region still under Kiev's control.

In a report, the OSCE mission reported 69 shots fired from tanks, as well as hundreds of mortar rounds fired. Heavy incoming artillery fire from separatist lines landed about 300 meters (328 yards) from the OSCE monitoring post, forcing them to relocate. The OSCE said it saw several rebel tanks and other armored vehicles massing in the area.

The continued fighting could pose another challenge for Kiev, which has struggled to turn from the war to accelerating economic and political overhauls.

Brussels has acknowledged a slew of initiatives in Ukraine in recent weeks to beef up the fight against corruption, hand money and some powers to the regions and liberalize the energy sector.

One senior EU official said Monday that the bloc's continued financial support depended on continued momentum in Kiev in driving the domestic reforms.

The bloc has so far agreed to EUR3.4 billion ($3.7 billion) in balance of payments assistance for Ukraine, around half of which has been disbursed. The EU has said it could eventually make up to EUR11 billion available through various loans and grants in coming years.

The official said that Ukraine must be "beyond reproach" on fulfilling its obligations under February's Minsk cease-fire agreement so as not to give any room for Russia to renege on its commitments. That includes amending Ukraine's constitution to allow greater autonomy for the east.

The weekend fighting around Mariupol was a "stark reminder," the official said of the continued threat posed by the separatists and their Russian backers, showing the importance of Ukraine doing its part to hold the cease-fire in place.

The EU is expected to announce some stepped-up assistance for longstanding efforts to clean up the area around the Chernobyl nuclear site and to help smaller Ukrainian firms win investment.

However Mr. Juncker and Mr. Tusk are unlikely to meet Mr. Poroshenko's demands for an EU peacekeeping presence in eastern Ukraine or for quicker progress on granting Ukrainians visa free access to the 28-nation bloc, a priority issue for Ukraine.

There is "no appetite for sending peacekeepers," the official said.

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