Aid groups were unable to deliver much-needed food packages to four besieged towns in war-torn Syria on Monday, the International Committee of the Red Cross said, citing security problems, AFP reports.

Since an unprecedented ceasefire took effect on February 27, aid deliveries have reached thousands of people in areas blockaded by both regime and opposition forces.

Under an agreement negotiated with the two warring sides in the five-year war, aid groups were set to deliver aid to Madaya and Zabadani, two towns near Damascus blockaded by the regime, and Fuaa and Kafraya, which are besieged by rebels in Syria's northwest.