**A gun battle has broken out between Afghan security forces and militants in the southern city of Lashkar Gah, officials say.**Rocket fire and explosions could be heard from an area close to the army barracks. Some reports say militants entered buildings in the vicinity.
Extra troops have been deployed and attack helicopters are over the city and firing on insurgents, Nato said.
The Taliban insurgency is at its fiercest in south and east Afghanistan.
Lashkar Gah is the capital of Helmand province where militants frequently launch attacks on security forces.
UK and other Nato troops are set to launch the biggest operation yet in Helmand, the BBC learned on Monday