Sanaa, June 2: Heavy shelling north of Yemen’s capital threatened to close the main international airport today as bloody street battles between government troops and tribesmen appeared to escalate.

The airport, which lies roughly 9km north of the capital, Sanaa, was open today and flights operated normally, the airport director, Naji Quddam, said in a statement, denying news reports that it had closed.But the main road to the airport from Sanaa remained dangerous to navigate because of government checkpoints, sporadic shelling and heavy fighting in the north of the city.

There, large numbers of tribal fighters surging south towards Sanaa squared off against Yemeni troops at an important checkpoint in fighting that raged overnight and today. The northern checkpoint is a major barrier between the capital and Amran province, a stronghold of the tribesmen loyal to the Ahmar family who have been battling the government for 10 days.