Istanbul, Turkey (CNN) -- A separatist rebel group claimed responsibility Friday for an ambush on a convoy connected with Turkish Prime Minister Recep Tayyip Erdogan.
At the time of the attack Wednesday, Erdogan was not in the convoy, which had been traveling to a campaign rally, and he was airlifted to his next stop in a helicopter.
A policeman was killed and another was injured in the attack, Erdogan said Wednesday.
In a statement e-mailed to CNN, the Kurdistan Workers Party, or PKK, claimed responsibility for the ambush in the province of Kastamonu.
The statement reads: "On 4 May at 17:15 hours, our guerrillas carried an action against a police vehicle in a vehicles convoy at 25th km of the Kastomonu-Ankara Highway skirts of the Mount Ilgaz. This action carried out in retaliation against the police terror against civilian population."
The attack was in northern Turkey, between the cities of Kastamonu and Cankiri.
A bomb exploded in front of the police vehicles escorting the ruling Justice and Development Party bus after it made a stop in Kastamonu. Erdogan and his contingent were on a campaign trip ahead of parliamentary elections, expected to be held on June 12.
PKK rebels have been battling the Turkish state since the early 1980s. More than 30,000 people, most of them ethnic Kurds, have been killed in the conflict.
Riots erupted in Turkey's largest city, Istanbul, last month, after Turkey's electoral board issued a controversial decision to ban several Kurdish politicians from running for office. The electoral board later reversed its decision.
Addressing a rally in Amasya, Erdogan expressed sorrow about the death and blamed the attack on separatist groups.
"These dark minds who do not believe in democracy's struggle. These terrorists, these separatist forces believe they can only achieve results this way instead of through the ballot box," the prime minister said.