The U.N. Security Council is considering a draft resolution to condemn the "shooting down" of a Malaysian passenger plane in Ukraine, demand armed groups allow access to the crash site, and call on states in the region to cooperate with an international investigation.

Australia - which lost 28 citizens - circulated a draft text, seen by Reuters, to the 15-member Security Council late on Saturday and diplomats, speaking on condition of anonymity, said it could be put to a vote as early as Monday.

The draft resolution "demands that those responsible for this incident be held to account and that all states cooperate fully with efforts to establish accountability."

It "condemns in the strongest terms the shooting down Malaysia Airlines flight MH17 ... resulting in the tragic loss of 298 lives" and "demands that all states and other actors in the region refrain from acts of violence directed against civilian aircraft."

The United States and other powers have said the plane was likely brought down on Thursday by a surface-to-air missile fired from rebel territory.

Russia's U.N. mission declined to comment on the draft Security Council resolution.

The Security Council issued an statement on Friday calling for a "full, thorough and independent international investigation," access to the site and appropriate accountability. Britain drafted the short text and hoped the council could issue it on Thursday but Russia requested more time to review it.

Meanwhile, a top Ukrainian rebel leader said on Sunday that the pro-Russian fighters will guarantee the safety of international monitors at the Malaysian jet's crash site if Kiev agrees to a truce.

"We declare that we will guarantee the safety of international experts on the scene as soon as Kiev concludes a ceasefire agreement," the self-proclaimed Donetsk People's Republic's deputy premier Andrei Purgin said in a statement.

Monitors gain better access to crash site

International monitors have now been allowed to visit more of the crash site, though gunmen still stopped them approaching some of the wreckage.

In sometimes tense scenes with pro-Russian rebels clearly uncomfortable at having observers and the press present, a top official at the Organisation for Security and Cooperation in Europe said access had improved since they arrived on Friday.

Securing the site and preserving evidence is crucial for investigators to try to piece together what, and who, caused the airliner to plunge into the steppe.

"We have now had the possibility to see a bit more of this rather large scene. We have observed the situation here as it was presented to us," said Alexander Hug, deputy chief monitor of the OSCE special monitoring mission to Ukraine.

"We also had the possibility to speak to those who are in charge here, and ... to speak to inhabitants of a local village.

"As in any job, the cooperation improves over time ... we had better access today."

On Friday, a group of monitors were hampered in their work by "armed personnel who acted in a very impolite and unprofessional manner".

"Some of them even looked slightly intoxicated," an OSCE spokesman said.

On Saturday, gunmen formed a line along the edge of the fields where the plane crashed, ostensibly to show they were securing the site.

World leaders have called for a rapid investigation into the disaster, which could mark a pivotal moment in deteriorating relations between Russia and the West.

Dutch prime minister Mark Rutte has said Russian president Vladimir Putin has "one last chance" to show he is serious about helping rescuers recover the bodies of the victims.

"I was shocked at the pictures of utterly disrespectful behaviour at this tragic spot," he said, referring to allegations that bodies of the passengers were being dragged about and allowed to rot at the scene.

Malaysia 'deeply concerned' site is not secured

The confusion over access to the area came as Malaysian transport minister Liow Tiong Lai called for the crash site to be secured amid claims evidence had been removed.

"On investigation, Malaysia is deeply concerned that the crash site has not been properly secured," he said.

"The integrity of the site has been compromised and there are indications that vital evidence has not been preserved in place. Interfering with the scene of the crash risks undermining the investigation itself.

"Any action that prevents us from learning the truth about what happened to MH17 cannot be tolerated. Failure to stop such interference will be a betrayal of the lives that we lost. Malaysia calls for all parties to protect the integrity of the crash site and to allow the investigation to proceed.

"Since the plane went down, the remains of 298 people lie uncovered. Citizens of 11 nations, none of whom are involved in the conflicts in eastern Ukraine, cannot be laid to rest. Their lives were taken by violence. Now violence stops them being accorded their final respect. This cannot continue."

Mr Liow said a special team from Malaysia had arrived in Kiev and were asking for support from the Ukrainian government.

The chief executive of Malaysia Airlines is already in Kiev.

Mr Liow also defended the flight path of MH17 saying it is a busy path like a major "highway in the sky" and the plane never strayed into restricted air space.

There is no confirmation if the black box from MH17 has been located although earlier reports from Ukraine claimed rebels had it in their possession.

Russia places blame with Kiev

Russia has fought back against claims of its involvement in the downing of MH17, instead implying the government in Kiev might be responsible.

Russian deputy defence minister Anatoly Antonov went on national television to reel off a list of 10 "simple" questions for the Ukrainian government, which he said were key to determining who shot down the Malaysian airline.

"Answers to these questions would allow all of us, not only in Russia but also in the West and the east, in Asia, to try and find an answer to the most important question: what happened in the sky over Ukraine and what we need to do so that this does not happen again," Mr Antonov said.

He said Kiev should release details regarding its alleged use of Buk missile systems in eastern Ukraine, and explain why they were being operated if separatists do not possess aircraft.

The Russian defence ministry on Friday claimed the radars of Ukraine's Buk missile systems - the weapon thought to have been used to shoot down the jet - were in use on the day of the crash.

He also wondered why Ukrainian air-traffic controllers had allowed the passenger jet to stray to the north, in the direction of a conflict zone.

Both Russia and Ukrainian forces have variants of the Buk, a surface-to-air missile believed to be the most likely culprit for the downing of the jet.

Ukrainian prime minister Arseny Yatseniuk hit back, telling a German newspaper that it takes professionals to shoot down an airliner and not a group of "drunken gorillas", suggesting that Russia was behind the incident.

A spokesman for Ukraine's security council also said on Saturday that 15 pieces of military equipment had been brought over the border from Russia into the eastern region of Luhansk overnight.

US president Barack Obama called the loss of flight MH17 a "wake-up call" to Europe to join the United States in threatening Moscow with heavier economic sanctions if it does not use its influence to help end a conflict that has driven the gravest East-West confrontation since the Cold War.

Russia's foreign ministry says Moscow will retaliate after Washington imposes new sanctions over Ukraine and will also impose visa restrictions on a similar number of US citizens.

A map shows the path of Malaysia Airlines flight MH17, which was shot down over Ukraine on July 17, 2014, killing 298 people. ( ABC News )

ABC/wires