* Assault on Kunduz a year after city fell briefly to Taliban
* Fighters take up position in residents' houses
* Security forces under pressure as Helmand fighting intensifies

Taliban fighters attacked the northern Afghan city of Kunduz overnight, entering urban areas and threatening a repeat of the assault in which they seized the city exactly a year ago.
Sheer Ali Kamawal, commander of the 808 Tandar police zone in Kunduz, said the attack began at around midnight and fighting was going on in and around the city. Some Taliban fighters had entrenched themselves in homes.
The fighters appear to have slipped through a defensive security line set up around Kunduz, entering the city itself before clashes broke out, witnesses in the city said.
In Kabul, Brigadier General Charles Cleveland, spokesman for Afghanistan's Nato-led force, said he was aware of reports of sporadic fighting in Kunduz but said he had not seen evidence of a major Taliban offensive.
"At this point, we are not observing evidence via our internal means to support the reports that Kunduz is under significant attack," he said in an emailed statement.
Police spokesman Mahfozullah Akbari said security forces were preparing to drive out the fighters, who had infiltrated the Khak Kani area in the city's southwest.
"The Taliban are inside some civilian houses and we have to carry out operations very carefully," he said.
The interior ministry said reinforcements were being sent.
Military helicopters flew overhead and gunfire could be heard in Kunduz, where a year ago to the day, Afghan troops backed by US air strikes and special forces battled to drive out Taliban who had raised their flag in the city centre.
On Monday, a Reuters reporter saw at least five Taliban fighters armed with AK-47 assault rifles, machine guns and rocket-propelled grenades in the city. He saw fighters entering homes and taking up position on roofs.
The attack, a day before the start of a major donor conference in Brussels, underlines Afghanistan's precarious security. Government forces are estimated to have control over almost two-thirds of the country.
Taliban spokesman Zabihullah Mujahid said in his official Twitter account four government checkpoints in Kunduz had been captured and some soldiers had been killed.
"A massive operation started on Kunduz capital from four directions early this morning," he said.
Attacks across Afghanistan
The attack came as the Taliban stepped up attacks in different parts of Afghanistan, including the southern province of Helmand, where they have been threatening the provincial capital of Lashkar Gah.
On Monday, Taliban fighters, positioned just across the Helmand river from the centre of Lashkar Gah, also took control of Nawa district to the south, killing a district police chief, officials said.
Heavy fighting has also continued along the main highway to Tarin Kot, the provincial capital of Uruzgan, also in the south, where a Taliban raid on September 8 sparked fears of another collapse like that in Kunduz last year.
The raid on Tarin Kot was beaten back but alarmed security officials because the militants were able to enter the city without significant resistance after police abandoned dozens of checkpoints.
The fall of Kunduz last year was one of the most serious blows suffered by the Western-backed government in Kabul since the withdrawal of most international troops at the end of 2014.
Although the insurgents abandoned Kunduz after a few days, their capture of a provincial capital underlined their growing strength and exposed flaws in Afghan security forces.
Afghanistan's international partners are expected to approve maintaining billions of dollars in funding for the government over the next four years at the two-day Brussels meeting.