"Mr Putin, stop this senseless war! We are ready for talks, we are ready to speak with one another about ending this war. But these barbaric attacks on the civilian population of Ukraine must stop," Merz said.
Merz visited the National Academy of Sciences in Kyiv, which was struck in a Russian drone attack last Monday, accompanied by Ukrainian President Volodymyr Zelenskiy.
Speaking at the ruins, Merz described Russian attacks on civilian targets as "daily war crimes" and renewed his appeal to Putin.
"We can talk but only when the weapons fall silent - and the weapons must fall silent," he said.
The drone attack on the academy killed one woman and injured about six people.
The impact and subsequent fire destroyed two floors of the historic building, located about 140 metres from the German embassy.
Russian attacks triggered several drone alarms during Merz's visit on Sunday while a drone struck Kyiv's Northern Bridge, about 5km from where the chancellor was staying.
At a joint press conference with Zelenskiy, Merz said Russian warnings and attacks would not deter him from visiting Ukraine.
"We will not be intimidated," he said.
"Nor will we be intimidated by a drone attack taking place at the same time as our visit."
The Russian foreign ministry had urged foreigners to leave Kyiv ahead of expected attacks.
Merz said he did not know whether Russia's warnings were directly linked to his visit but said they would not influence his travel plans.
"I make the trips that I deem appropriate," he said.
Merz said he was aware of three drone alerts during his stay but had not been taken to a shelter.
Russian strikes were also reported elsewhere in Ukraine on Sunday.
Authorities in the northeastern Sumy region said five people were injured when a Russian glide bomb struck a residential building.
A medical supplies warehouse was also hit, killing one person, Zelenskiy said.
A telecommunications company in Dnipro was struck, leaving six people injured.
Russia launched 135 drones, according to Ukrainian figures.
Zelenskiy said Russia had used more than 1900 attack drones, 1700 glide bombs and 25 missiles against Ukraine over the past week.
Russia's defence ministry meanwhile announced plans to further intensify strikes on Kyiv and other parts of Ukraine, saying Russia is responding to threats by Zelenskiy to attack more military sites and arms facilities inside Russia.
The ministry said Zelenskiy bore "full personal and political responsibility" for the escalation.
Ukraine has significantly expanded its attacks on oil refineries and other targets inside Russia in recent months, aided by financial and military support from its allies.
Merz pledged further military and financial support for Ukraine, with German government sources saying it will include thousands of interceptor drones and accelerated production of long-range weapons.
"If Russia is not stopped, its war machine will sooner or later turn against us," Merz said after arriving in Kyiv by train.
Ukraine has been defending itself against Russia's full-scale invasion since February 2022.
with Reuters
