A fissure eruption started in Holuhraun, north of Dynjujökul around midnight.
Seismic activity has decreased as a result of the pressure release, however a significant amount of earthquakes is still detected in the magma dike, between the eruption site and south to about 5 km into Dyngjujökull.
Strongest events were 3.8 in the caldera of Bárðarbunga at 04:37, as well as 2.9 at 05:39 and 3.5 at 06:38 in the dike. These earthquake are very closely monitored, but no significant change volcanic activity following these has been observed so far.
The color aviation code for Bárðarbunga was raised to red (eruption is imminent or in progress - significant emission of ash into atmosphere likely) during the night, and brought back to orange (Volcano shows heightened or escalating unrest with increased potential of eruption) this morning. In the meanwhile, Askja volcano (roughtly 50 km NE of Bárðarbunga) has switched from green (Volcano is in typical background, non-eruptive state) to yellow (Volcano is exhibiting signs of elevated unrest above known background level).
Source: IMO
You can wacth the eruption here.