KYIV, Ukraine (AP) — Ukrainian forces and Russia-backed rebels in eastern Ukraine began a prisoner exchange on Thursday, according to the Ukrainian president's office and separatists.

The exchange comes as part of an agreement brokered last year at a summit of the leaders of Ukraine, Russia, Germany and France. The aim is to take confidence-building steps that could lead to an end of the six-year war in eastern Ukraine, which has killed more than 14,000 people and aggravated tensions between Russia and the West.

Ukraine hopes to take back 19 of its citizens in the swap with the two separatist entities in the rebel-controlled east, according to a statement from the office of Ukrainian President Volodymyr Zelenskiy. It was not immediately clear how many rebels would be released in total.

It was the third prisoner exchange since Zelenskiy was elected in a landslide last year on promises of ending the conflict, which began in 2014.

“The current exchange demonstrates the effectiveness of the president’s strategy and compliance with the agreements reached at the summit,” the statement read.

Separatist officials in the self-proclaimed Donetsk People’s Republic said they turned over nine Ukrainians on Thursday in exchange for 10 rebels. They said one more rebel refused to return to rebel-controlled Donetsk.

Another exchange, with the self-proclaimed Luhansk People’s Republic, is scheduled for Thursday afternoon.

The last major prisoner swap between separatist rebels and Ukrainian forces took place in December 2019, with the two sides exchanging 124 rebels for 76 Ukrainians.