Baghdad, April 25 : Four Katyusha rockets landed near a Turkish military base in Iraq's northern province of Nineveh, without causing casualties, a local official said. The rockets, fired by unknown militants on Sunday evening, targeted the Bashiqa base housing Turkish forces in the Zlikan area, nearly 400-km north of Baghdad, Mohammed Amin Gharib, Mayor of the Zlikan area, told Xinhua news agency. No group has yet claimed responsibility for the attack, Xinhua news agency reported. Iraq has repeatedly accused Turkey of violating its sovereignty by entering its territory without permission, including Turkey's military presence in the Bashiqa base. On April 18, Turkish forces launched a new ground and air cross-border operation against the outlawed Kurdistan Workers' Party (PKK) in northern Iraq. The PKK, listed as a terrorist organisation by Turkey, has been rebelling against the Turkish government for more than 30 years. Turkey regularly conducts cross-border operations on the PKK bases in northern Iraq, despite Iraq's repeated protests. /IANS