The Ukrainian army says it has seized a key town near the rebel stronghold of Donetsk, as fighting rages in the east.

Pro-Russia separatists were driven out of Avdiivka today, the army said. The strategic town is near the airport and train station in Donetsk.

Heavy fighting around Donetsk has again prevented international experts from reaching the crash site of flight MH17.

Details of fresh EU sanctions against Russia for its support to the Ukrainian rebels are expected shortly.

Almost two weeks after the Malaysia Airlines jet came down, international monitors were turned back to the city of Donetsk at a separatist checkpoint, with smoke rising in the distance from fighting.

Regional officials in Donetsk said today that 19 people had been killed in fighting in the past 24 hours.

Ukraine says its troops have also entered the towns of Shakhtarsk and Torez in Donetsk region, and Lutuhyne in Luhansk region.

"If Russia continues on this current path, the costs on Russia will continue to grow," said US President Barack Obama, announcing the new round of sanctions.

In a statement today, Russia's foreign ministry said the new US sanctions were "destructive and short-sighted".

"Such decisions by Washington can bring nothing but further aggravation of US-Russia relations," the statement said.

The first sign of retaliation came after Russia announced a ban on most fruit and vegetable imports from Poland.

Russia buys more than €2bn worth of EU fruit and vegetables a year, making it by far the biggest export market for the products.

Polish fruit growers said the ban was political but Russia said the move was for sanitary reasons.

Meanwhile, Germany's Economy Minister Sigmar Gabriel said the sanctions could hurt the German economy, which has strong trade links with Russia.

"Nonetheless at a time of war and peace, economic policy is not the main consideration," he told journalists.