Donetsk, Ukraine: A team of international police officers that had planned to start searching for evidence and the remaining bodies at the site of the Malaysian plane disaster in eastern Ukraine cancelled their trip on Sunday after receiving reports of fighting in the area.

Alexander Hug, the deputy head of a monitoring team from the Organisation for Security and Cooperation in Europe, said it was too dangerous for the unarmed officers to travel to the site from its current location in the rebel-held city of Donetsk.

Malaysian Airlines Flight 17 was shot down with a surface-to-air missile over a part of eastern Ukraine controlled by pro-Russian separatists on July 17, killing all 298 people on board. US and Ukrainian officials say it was shot down by a missile from rebel territory, most likely by mistake.

While it was not immediately clear where precisely clashes had broken out, a Ukrainian defence official said on Sunday that government forces are now undertaking efforts to clear the areas around the Boeing 777 crash site from separatist rebels.

Hug said the police mission, comprising officers from the Netherlands and Australia, will reconsider resuming operations if security improves. Malaysian experts are also due to join them next week.

“We continue to reassess the situation and we will start to redeploy tomorrow morning back to the site if the situation changes,” Hug said.

Australian prime minister Tony Abbott had said earlier on Sunday that unarmed Australian police would be part of the Dutch-led police force to secure the area and help recover victims’ remains.

Abbott said that by using unarmed police, Ukraine’s Parliament will not need to ratify the deployment as it would if the security force were to be armed.

“This is a risky mission. There’s no doubt about that,” Abbott told reporters. “But all the professional advice that I have is that the safest way to conduct it is unarmed, as part of a police-led humanitarian mission,” he said.

Malaysian Prime Minister Najeeb Razak said in a statement that his country would send dozens of police and that his country had received assurances from pro-Russia separatists that they would provide protection for investigators.

Ten days after the disaster, a full-fledged investigation still has not begun at the site, compromising evidence and leaving some bodies still unrecovered. Concerns about the integrity of the site were raised further when a couple that had flown from their home in Perth, Australia, visited the wreckage-strewn fields on Saturday outside the village of Hrabove and even sat on part of plane’s wreckage.

Flights from Ukraine to the Netherlands have taken 227 coffins containing victims of the plane disaster. Officials say the exact number of people held in the coffins still needs to be determined by forensic experts in the Netherlands.

Ukraine’s National Security Council spokesman Andrei Lysenko said that Ukrainian troops were engaging rebels in fighting at several locations Sunday, including near the town of Debaltseve, which is 15 miles (25 kilometres) northwest of the crash site.

There was also fighting on the outskirts of Horlivka, one of the separatists’ key strongholds, Lysenko said.

Lysenko said more than 20 rebel fighters were killed and eight of their armored vehicles destroyed during fighting in Horlivka. One government soldier was killed in the previous day’s fighting, he said.

Russian state news agency RIA Novosti reported on Sunday that a column of Ukrainian armored personnel carriers, trucks and tanks had entered the town of Shakhtarsk, 10 miles (15 kilometres) west of the site of the crash.

Shakhtarsk is a strategic town in the area. By controlling the town, the Ukrainian army would be cutting off the regional capital, Donetsk, from the highway leading to the Russian border.

The Malaysia Airlines disaster prompted some expectations in the West that Russia would scale back its involvement in the uprising in Ukraine’s east, but the opposite seems to be the case.

Ukraine and the United States have accused Russia of launching artillery attacks onto Ukrainian soil in recent days. These claims have not been definitively verified.

Meanwhile, the United States said it has seen powerful rocket systems moving closer to the Ukraine border.

In Warsaw, about 250 people marched through the city to protest what they called the “terror” imposed by Russian President Vladimir Putin in Ukraine. Some of the demonstrators carried Ukrainian flags, and there were banners that proclaimed “Putin is a Sponsor of Terror” and “Europe, Stop Just Talking. Start Taking Action! Stop Terror in Ukraine.”