The Bashar Assad regime is preparing an offensive to retake southern Syria and the Syrian Golan Heights from rebel groups and has reportedly placed tanks and heavy artillery inside the demilitarized buffer zone on the country’s border with Israel.

The step violates the Agreement on Disengagement signed in 1974 between Israel and Syria, which concluded the Yom Kippur War. Israel is expected to complain to the United Nations peacemaking force known as UNDOF, the Haaretz daily reported Thursday.

The United Nations Disengagement Observer Force has patrolled the buffer zone between Syria and Israel since 1974, a year after the war ended. For nearly four decades, UNDOF helped enforce a stable truce between the two countries, but the Syrian civil war has now spilled into the area, according to the report.

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Since most UN staff have been moved out of Syria due to the bloody war and are now watching at a safe distance from Israel, it is unclear if the international body can force the Assad regime to halt its military presence in the buffer zone.

The six-year conflict has seen not only some intense fighting in the buffer zone but the abduction of peacekeepers by al-Qaeda-linked anti-Syrian government militants, and other attacks that prompted several countries to withdraw their soldiers.

Israel has tried to stay out of the civil war in Syria and refrained from taking sides, but has responded to spillover fire on numerous occasions and warned the Assad regime against attack.

The Haaretz report said there is almost no Iranian presence near the Israel-Syria border. However, Lebanese terror group Hezbollah has established a Golan regional command center, with a hundred of its operatives located in south Syria and a thousand other local residents being paid regular salaries by the organization, it said.

Israel was said to recognize an interest by Hezbollah in the border and initial attempts to establish military infrastructure there.

Israel captured the Golan Heights from Syria in the 1967 Six Day War and later extended civil law over the strategic plateau overlooking northern Israel, in a move that is not internationally recognized.

Last year, the UN Security Council strongly condemned fighting in the buffer zone and urged the Syrian government and opposition groups to withdraw from the area.

The resolution backed Secretary-General Antonio Guterres’ findings that ongoing military activities in the area of separation have the potential to escalate tensions and jeopardize the ceasefire between Israel and Syria, and pose risks to civilians and UN personnel on the ground.

The resolution condemned the use of heavy weapons, including tanks, by both the Syrian armed forces and armed groups in the area of separation.

It underscored the need for UNDOF to have the sophisticated equipment and technology to effectively monitor the area of separation and ceasefire line including the capability to counter improvised explosive devices and “a sense and warn system, to ensure the safety and security of UNDOF personnel and equipment.”

According to the UN peacekeeping department, the UNDOF mission has 959 personnel including 828 military.

AP contributed to this report.