SEOUL, July 15 (AFP) - South Korea's President Yoon Suk Yeol was in Ukraine Saturday on an unannounced visit, his office said, where he visited the town of Bucha ahead of a summit with Ukrainian leader Volodymyr Zelensky.

"The president first toured the Bucha city massacre site near the capital Kyiv and the city of Irpin, where missile attacks were concentrated on civilian residential areas," his office said.

"President Yoon will visit a memorial for the war dead to lay a wreath, and hold a summit meeting with President Zelensky," it added in a statement.

South Korea, the world's ninth-largest arms exporter, has sent humanitarian assistance to Ukraine and has also sold tanks and howitzers to Poland -- a key ally for Kyiv as it battles invading Russian forces.

However, it has a long-standing policy of not providing weapons to active conflict zones, which it has stuck to despite repeated requests from the United States, European allies and Ukraine itself for more help.

Yoon's meeting with Zelensky -- who has previously urged Seoul to consider supplying weapons to Kyiv directly -- is expected to focus on South Korea's supply of aid to the country.

Seoul, which remains technically at war with nuclear-armed North Korea, produces significant volumes of NATO-compatible weaponry, including its tanks, howitzers and deeply sought-after shell ammunition.

Seoul has hinted that it could reconsider its policy of not supplying lethal aid, with Yoon saying earlier this year that a large-scale Russian attack on civilians could tip the balance.

But in May, South Korea dismissed a US media report that its artillery rounds were heading to Ukraine, saying its position on not providing lethal aid to Kyiv was unchanged.

But experts warn that South Korea is in a tricky position because of its economic ties with Russia -- its 15th largest trading partner as of 2022 -- as well as Moscow's influence over North Korea.