<?xml version="1.0"?>
<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4/A</documentType>

    <periodOfReport>2004-01-08</periodOfReport>

    <dateOfOriginalSubmission>2004-01-09</dateOfOriginalSubmission>

    <issuer>
        <issuerCik>0001098402</issuerCik>
        <issuerName>VIA NET WORKS INC</issuerName>
        <issuerTradingSymbol>VNWI</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001077832</rptOwnerCik>
            <rptOwnerName>GESMAR-LARSEN JAN</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>H. WALAARDT SACRESTRAAT 401</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>1117 BM SCHIPHOL-OOST</rptOwnerCity>
            <rptOwnerState>P7</rptOwnerState>
            <rptOwnerZipCode></rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>1</isDirector>
            <isOfficer>0</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>
        <derivativeTransaction>
            <securityTitle>
                <value>Options to Purchase Common Stock</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>2.00</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2004-01-08</value>
                <footnoteId id="F1"/>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionAmounts>
                <transactionShares>
                    <value>25000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F2"/>
            </exerciseDate>
            <expirationDate>
                <value>2014-01-07</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>25000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>25000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
                <natureOfOwnership>
                    <value></value>
                </natureOfOwnership>
            </ownershipNature>
        </derivativeTransaction>
    </derivativeTable>

    <footnotes>
        <footnote id="F1">This amended Form 4 is being filed to clarify that the date of the transaction was January 8, 2004, not August 1, 2004, and to clarify that no cash consideration was paid for the option, which was issued in consideration of the reporting person's services to the issuer as a director.</footnote>
        <footnote id="F2">1/3 of the shares subject to this option become exercisable on January 1, 2005.  The remaining shares subject to this option become exercisable in equal  instalments over the subsequent 24 month period beginning on  February 1, 2005.</footnote>
    </footnotes>

    <remarks></remarks>

    <ownerSignature>
        <signatureName>Matt S. Nydell, Attorney in Fact</signatureName>
        <signatureDate>2004-02-09</signatureDate>
    </ownerSignature>
</ownershipDocument>

