Defence Secretary Michael Fallon is expected to announce a "significant increase" in troops sent to the Falkland Islands amid fears that Russia is helping to arm Argentina.

Russian President Vladimir Putin is believed to be working on a deal to lease 12 long-range bombers to Argentina, 33 years on from the Falklands War.

Fallon's decision reflects "operational judgments" and the "increased nature of the threat", a Whitehall source told The Sun last night. "We want the people of the Falklands to know they are uppermost in our thinking," they said.

The increase in personnel and equipment will bolster the 1,200 troops already stationed in the Falklands. Four RAF Typhoon jets, a small fleet of Sea King search and rescue choppers and a Rapier anti-aircraft missile battery are also stationed on the islands.

Sir Gerald Howarth, a Tory MP and former defence minister, said he was "delighted" that the government was demonstrating its "unwavering commitment to the Falkland Islands so Argentina can be left in no doubt they are British sovereign territory and are deterred from repeating the folly of 1982".

He added that the threat had increased and Argentina's President Cristina de Kirchner had become ever more unpopular. "Who knows what she will do?" he said.

The Sunday Express reported in December that Russia was planning to offer Argentina 12 Sukhoi Su-24 Fencer aircraft in exchange for beef and wheat to beat EU sanctions over Ukraine.

The Sun says a potential new "oil bonanza" from exploratory drilling in Falklands territorial waters would also make a new invasion "much more profitable".

It comes as MPs on the Defence Select Committee urged the government to maintain the Nato target of spending two per cent of national income on defence. The UK urgently needs to rebuild its defence capabilities in the face of the growing threat from Russia, they said.