British police dispersed hundreds of protesters who blocked access to an oil exploration site in rural England on Monday in an intensification of an almost month-long standoff over the nascent shale gas extraction industry in Britain.

A total of 36 people were detained, both in the village of Balcome and in London, in the first of two days of "direct action" against fracking, which protesters fear may trigger small earthquakes and pollute water supplies.

Hundreds of protesters converged on the West Sussex village and repeatedly scuffled with around 400 police who were bussed in from 10 different forces around Britain.

While many played drums and sang, others chained themselves to each other at the entrance of the Cuadrilla Resources-owned site, behind tall metal fences down a country lane bordered by dense woodland.

"This protest is part of a huge wave that's building up," 32-year-old Mark Weaver from London told Reuters. "There's a lot of people who are going to be watching what's happening here."

Desperate to stimulate a U.S.-style production boom and offset dwindling North Sea oil and gas reserves, the Conservative-led government has backed fracking as an "energy revolution" that can create jobs and lower energy prices.

Activists argue the government should invest in renewable energy rather than fracking, the retrieval of gas and oil from rock by injection of high-pressure water, sand and chemicals.

Caroline Lucas, Britain's only elected Green Party member of parliament, was among those detained. "Along with everyone else who took action today, I'm trying to stop a process which could cause enormous damage for decades to come," she said.

Anger

Thirty people were detained after protesters refused to move from the entrance of the Cuadrilla site in Balcombe, about 55 km south of London. The protests have already forced Cuadrilla to halt drilling at the site.

Six other people were detained in London after glueing themselves to glass doors at the public relations firm employed by the privately-owned energy company, chaired by former BP chief Lord Browne, and blocking the entrance.

Cuadrilla, which is drilling a conventional oil well in Balcombe, is the only company to have fracked a shale gas well in Britain, making its activities a target for protesters.

The debate has turned angry in recent weeks with death threats sent to the head of Cuadrilla and around 75 people arrested at the Balcombe site since protesters set up camp there in July, including those held on Monday.

With natural gas imports from outside the North Sea set to surpass domestic production by 2015, Britain has been looking for new gas sources to meet rising import needs, with an eye on the U.S., where a massive expansion of shale gas extraction has driven down energy prices and cut dependence on imports.

Imports for Britain have so far mostly come from Norway and, increasingly Qatar. Last year it imported around 50 billion cubic metres of gas via pipelines and liquefied natural gas (LNG) ships.

The country has potentially vast shale gas resources in underground rock formations; the government said last month there may be 1,300 trillion cubic feet of gas present in the north of England alone.

"Why would you want fracking on your doorstep?" said protester Melanie Strickland, 30, who works for a health charity. "It pollutes water, it causes earthquakes. It's profoundly undemocratic because it tends to happen without any consultation so I think there'll be resistance everywhere."