US commanders are weighing plans to send more American troops to northern Afghanistan, a region under the command of German forces, a US official said on Tuesday.

The likely deployment follows a rise in violent attacks by insurgents around Kunduz and elsewhere in regional command north, the official, speaking on condition of anonymity, told AFP.

German media have reported about 2,500 US troops would head north, including about 1,000 focused on training Afghan security forces.

But US and NATO commanders have yet to announce how many troops might be assigned to the north, which has been relatively calm compared to the country''s east and south.

"They (the Germans) asked for additional support," said the official.

US officers were now looking "at how many troops do we really need" in the north and what types of forces would be sent, the official said.