There is a heavy police presence on the streets of Port Moresby ahead of a Papua New Guinea Supreme Court decision on the constitutionality of the government.
The Prime Minister Peter O'Neill was elected by a parliamentary vote of 70 to 24 in August, dumping the long-time leader Sir Michael Somare.
Sir Michael's supporters immediately brought the matter before the courts, arguing there was no vacancy in the prime ministership despite a four-month absence by the 76-year-old political veteran, who had been recovering from heart surgery in Singapore.
Police roadblocks have been set up along Port Moresby's main highway, Champion Highway, at Jackson's airport and around the nation's courts and parliament.
The police commissioner Tom Kulunga says the heavy police presence is there in case there is a violent reaction to the decision by the five man bench.
Mr O'Neill yesterday applied to have Chief Justice Sir Salamo Injia dismissed from overseeing the case, the government's third attempt to do so.
If Mr O'Neill is found to have been in breach of the constitution, it could break his fragile coalition and lead to the formation of a new government.