Macedonian President Gjorge Ivanov has refused to grant a coalition of Social Democrats and ethnic Albanian parties a mandate to form a government, further escalating the country's long-running political crisis.

Wednesday's move came two days after opposition leader Zoran Zaev, head of the Social Democrats, had asked Ivanov to designate him as prime minister following weeks of negotiations in the wake of an inconclusive election in December.

Zaev formed the coalition, which holds a parliamentary majority, after agreeing to support a bill to enable wider use of the Albanian language.

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That was part of a platform for negotiations agreed by the Albanian parties with authorities in Albania's capital, Tirana, which Ivanov said made the pact inadmissible.

"As long as I am president, I will not give the mandate [to form the cabinet] to a party working against sovereignty," Ivanov said in a televised address, accusing Zaev of intent to violate the country's constitution.

Macedonia has been in political limbo since a corruption and surveillance scandal broke two years ago, eventually forcing the veteran leader of the nationalist VMRO-DPMNE, Nikola Gruevski, out of office in January 2016 after 10 years in power.

Ivanov is a close ally of the former prime minister, who allegedly ordered the illegal wiretapping of thousands of people in order to cement his grip on power.

'It's chaos'

Commenting on Ivanov's move, an official from the Albanian Democratic Union of Integration (DUI), the single largest ethnic Albanian party with 10 parliamentary seats, said: "It's a chaos".

The second biggest ethnic Albanian party, Bes, which has five seats, said it would hold an urgent meeting on Wednesday evening.

In December's snap election, VMRO-DPMNE won 51 seats to the Social Democrats' 49, leaving neither able to form the government without parties representing ethnic Albanians who make up one third of the population.

The VMRO-DPMNE had already tried but failed to form a coalition.

Thousands had protested Zaev's deal on Monday evening.