He said security forces are battling the Taliban on three different fronts, and the insurgents have launched several attacks on checkpoints around the provincial capital.
Afghan security force members inspect the site of attack in Nad Ali district of Helmand province, Afghanistan, March 14, 2018.
No group, including the Taliban, has claimed responsibility for the attack so far.
"We have asked the central government for additional troops before Farah city falls into the hands of the Taliban", Salehi said.
In Helmand Province, a suicide truck bomb struck a checkpoint, killing at least two border police officers, said provincial police chief General Abdul Ghafar Safi.
Four members of the National Directorate of Security, Afghanistan's spy agency, and three police were killed, she added.
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This comes a day after US Defense Secretary James Mattis held discussions with President Ashraf Ghani during his trip to Kabul on Tuesday where they discussed the peace offer that has been made to the Taliban and the offer of comprehensive talks to Pakistan.
Now is the best time for the Taliban to negotiate for peace, the top United States general in Afghanistan said Wednesday, warning that an increased air and ground campaign against the insurgents would only get worse.
However, the Taliban appears likely to miss that conference and have ruled out direct talks with the Western-backed government in Kabul, which they say is an illegitimate, foreign-imposed regime.
Asked whether the United States would be willing to talk directly with the Taliban, Mattis reiterated the USA position that the talks should be led by Kabul.
The Taliban 's silence has provoked repeated calls for a direct response to Ghani's proposal made at an worldwide conference in Kabul on February 28. He offered his full support to the Afghan-led reconciliation process, White said, noting that it is aimed at achieving lasting peace in Afghanistan.
Casualties of the Afghan security forces have risen since the beginning of 2015 when Afghan soldiers and police assumed full responsibilities of security from the United States and North Atlantic Treaty Organisation troops.