UNITED NATIONS/KIEV, July 30 (Xinhua) -- International calls mounted on Wednesday for an unimpeded access to the crash site of the Malaysia Airlines Flight MH17, as intensifying fighting near the sites has severely hampered investigation on the ground.

The downing of the jet on July 17, which killed all 298 people on board, has prompted the Netherlands, Australia and Malaysia to take joint actions to probe the accident. On Wednesday, the international investigators have been blocked from the site for four days due to fierce fighting between Ukraine troops and separatists in eastern Ukraine.

UN Secretary-General Ban Ki-moon on Wednesday called for an immediate cessation of hostilities near the crash site so as to allow the investigators, who were caught in the middle of the conflict in Donetsk, to enter the area and retrieve key pieces of evidence.

"The secretary-general is deeply disturbed to learn that forensic teams and international investigators in Donetsk who are tasked to probe the downing of Malaysia Airlines flight MH17 continue to be impeded from accessing the site and carrying out their critical work due to heavy fighting in the area of the crash site," said a statement issued here by Ban's spokesperson.

Noting that there were victims' remains yet to be found, Ban said, "The families of the victims of this horrific tragedy deserve closure and the world demands answers -- international teams must be allowed to conduct their work."

The UN Security Council adopted the Resolution 2166 unanimously on July 21, demanding "safe, secure, full and unrestricted access" to the MH17 crash site, and calling for full cooperation with the international investigation.

However, the resolution could hardly hold on the ground since its passage, with Moscow and Kiev pointing fingers at each other over the flare-up of tensions surrounding the area.

In Kiev, authorities said Wednesday that securing the access for international investigators to the crash site will be its top priority during the upcoming trilateral talks in Belarus aimed at settling the crisis in eastern Ukraine.