Ireland has imposed a flight ban on parts of its airspace, including Dublin, as ash from an Icelandic volcano drifts towards it, while a small section of British airspace over Scotland will also be closed in the coming hours, air authorities said today.

The new alerts should not disrupt aircraft overflying Ireland from Britain or Europe, or southern British airports including Heathrow, Europe's busiest air hub, authorities in the two countries said.

"Over-flights of Ireland from the UK and Europe are not expected to be impacted tomorrow and southern UK Airports (Heathrow etc. ) are not expected to be impacted," the Irish aviation authority said.

Meanwhile Britain's Civil Aviation Authority (CAA) warned airlines that "increased concentrations of volcanic ash in the atmosphere are forecast to cause limited airspace closures in Scotland" on Tuesday.

Airspace across Europe was closed down for up to a week last month after the eruption of Iceland's Eyjafjallajokull, but was re-opened after emergency talks between European governments, airlines and regulators.

The international airline industry body, IATA, said the shutdown cost carriers some 1.7 billion dollars (1.3 billion euros) and called on governments to pick up at least part of the cost, angered by their handling of the crisis.

Eurocontrol, the continent's air traffic control coordinator, said more than 100,000 flights to, from and within Europe had been cancelled between April 15 and 21, preventing an estimated 10 million passengers from travelling.