Unidentified armed men have seized two airports in Crimea overnight, causing Ukraine‘s new interior minister to talk of “a military invasion and occupation” by Russia.

Ukraine’s newly appointed top security official, Andriy Paruby, accused Moscow of commanding the armed groups. “These are separate groups … commanded by the Kremlin,” Paruby said in a televised briefing in Kiev.

In tandem, the Russian parliament began considering a law that would allow Moscow to add new territories to Russia in a simplified manner. There are fears that the Kremlin, unhappy with the events that led to President Viktor Yanukovych fleeing Kiev last weekend, is trying to sow unrest in the largely pro-Russian region.

Adding to the sense of alarm, the interim Ukrainian president, Oleksandr Turchynov, dismissed the head of the armed forces, Admiral Yuriy Ilin, on Friday.

Paruby, the newly appointed secretary of the National Security and Defence Council, said a state of emergency may be declared. “It is one of the options in the development of events,” he said.

This contingency would not necessarily involve the deployment of the army, he added. “We are looking for other more effective ways of localising the situation on the Crimean peninsula.”

According to Ukrainain legislation, a state of emergency can be introduced by parliament for a period of up to two months.

In Simferopol, groups of armed men arrived overnight at the main airport serving the region. They wore military fatigues with no insignia and refused to talk, though one told news agencies they were part of a self-defence unit who wanted to ensure that no “fascists” arrived in the region from Kiev.

At Sevastopol airport, a military airport that handles few commercial flights, a man who said he was a captain in the tactical aviation brigade but declined to give his name, told the Guardian there were about 300 people of unknown identity inside the airport. “We don’t consider it any invasion of our territory,” he said without elaborating.

He said the men looked like military, were wearing two different types of uniform and were armed with sniper rifles and AK-47s. “We don’t know who they are, nor where they’ve come from.”

He added that there were two large trucks inside. “They [the vehicles] looked like they could contain 50 people at a push, so how they got 300 people inside I don’t know,” he said

A Major Fidorenko, from the Ukrainian military based at the airport, said the Ukrainians had been in touch with the unknown gunmen, who said they were there “to prevent unwanted landings of helicopters and planes”.

In Kiev, the new interior minister, Arsen Avakov, wrote on Facebook: “I can only describe this as a military invasion and occupation.”

On Thursday, masked gunmen with rocket-propelled grenades and sniper rifles seized the parliament building and government offices in Simferopol. The Russian flag was raised above the parliament.

Yanukovych, who apart for a brief television interview has not been since in the week since he fled Kiev, is due to give a press conference in the southern Russian city of Rostov-on-Don on Friday afternoon. Russian government sources say they have offered “protection” to Yanukovych in Russia, though it remains unclear how he arrived in the country.

In further worrying signs for Kiev, Russia’s parliament began considering two new laws on Friday. One of them offers eased citizenship requirements for Russian-speaking Ukrainians, removing the requirement that they should have lived in Russia for an extended period, while the other makes it easier for Russia to add new territories to its existing boundaries.

The latter law, which appears to be aimed pointedly at the Crimea situation, says territories can be added by a local referendum “in the case that a foreign country does not have effective sovereign state authority”.

Sergei Aksenov, the new prime minister of Crimea, has said he does not recognise Kiev authorities and still believes Yanukovych to be the legitimate Ukrainian president.

At a roadblock on the way from Simferopol to Sevastopol, Vladimir Zhirinovsky, a nationalist Russian politician, said Russia was not planning to take Crimea. However, he made it clear that the Russians still saw Yanukovych as Ukraine’s legitimate president.

“Russia will help the economic situation in the south-east. We can provide fuel and gas at a cheap price,” he said. “The [military] manoeuvres in Russia were normal, they were nothing special. Crimea should decide its future for itself. We Russians don’t want to create the impression we will take Crimea. Yanukovych is the lawful president by the constitution and the only one who can sign a decree.”