<?xml version="1.0"?>
<ownershipDocument>
    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType><periodOfReport>2003-10-29</periodOfReport>
    <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>1.36</value></conversionOrExercisePrice><transactionDate><value>2003-10-29</value></transactionDate><transactionCoding><transactionFormType>4</transactionFormType><transactionCode>A</transactionCode><equitySwapInvolved>0</equitySwapInvolved></transactionCoding><transactionAmounts><transactionShares><value>100000</value></transactionShares><transactionPricePerShare><value>1.36</value></transactionPricePerShare><transactionAcquiredDisposedCode><value>A</value></transactionAcquiredDisposedCode></transactionAmounts><exerciseDate><value>2004-10-01</value><footnoteId id="F1"/></exerciseDate><expirationDate><value>2013-10-28</value></expirationDate><underlyingSecurity><underlyingSecurityTitle><value>Common Stock</value></underlyingSecurityTitle><underlyingSecurityShares><value>100000</value></underlyingSecurityShares></underlyingSecurity><postTransactionAmounts><sharesOwnedFollowingTransaction><value>100000</value></sharesOwnedFollowingTransaction></postTransactionAmounts><ownershipNature><directOrIndirectOwnership><value>D</value></directOrIndirectOwnership><natureOfOwnership><value/></natureOfOwnership></ownershipNature></derivativeTransaction></derivativeTable><footnotes><footnote id="F1">1/3 of the shares subject to this option become exercisable on October 1, 2004.  The remaining shares subject to this option become exercisable in equal  instalments over the next 24 month period beginning on  November 1, 2004.</footnote></footnotes><remarks/><ownerSignature><signatureName>Matt S. Nydell,  Attorney in Fact</signatureName><signatureDate>2003-10-31</signatureDate></ownerSignature></ownershipDocument>

