MADRID (AFP) - Gibraltar has imposed a second lockdown to slow soaring rate of virus cases, just days after a landmark deal to ensure post-Brexit fluidity along its border with Spain.

The measure, beginning at 10pm on Saturday (Jan 2), will remain in force for 14 days, meaning Gibraltar's 34,000 residents can only leave home for essential shopping, to work, exercise or for medical reasons.

Over the past month, the number of cases in this tiny British enclave at the southern tip of Spain has more than doubled, rising to 2,304, up from 1,035 cases on Dec 2, Chief Minister Fabian Picardo said.

"The numbers of new infections with Covid-19 in our community are remarkably high and concerning," he told a news conference, saying that the virus was spreading "more quickly than we can control it".

Officials are concerned that the soaring rate of infections may be linked to the new coronavirus variant which emerged in the United Kingdom in November although so far, Gibraltar has only confirmed one such case.

"The behaviour of the virus with such massive infectivity suggests that we are seeing the new, more infectious variant at play here. But we cannot confirm that genetically," Mr Picardo said.

Gibraltar registered its first death from Covid-19 only on Nov 11, but that figure has now risen to seven.

Despite its proximity to hard-hit Spain, which has counted nearly two million cases and more than 50,000 deaths, Gibraltar has not imposed any restrictions on its border, which is crossed daily by 15,000 workers.

Although the frontier will remain open, movement will be restricted to essential work or medical reasons.

Gibraltar is set to roll out its vaccination programme on Jan 9 using the Pfizer vaccine.

The lockdown came two days after London and Madrid reached an agreement that will see Gibraltar included in the European Schengen zone to keep movement fluid on its border in a landmark deal just hours shy of the final Brexit deadline.